Chemical derivatization of single-wall carbon nanotubes to facilitate solvation thereof; and use of derivatized nanotubes to form catalyst-containing seed materials for use in making carbon fibers

ABSTRACT

This invention is directed to making chemical derivatives of carbon nanotubes and to uses for the derivatized nanotubes, including making arrays as a basis for synthesis of carbon fibers. In one embodiment, this invention also provides a method for preparing single wall carbon nanotubes having substituents attached to the side wall of the nanotube by reacting single wall carbon nanotubes with fluorine gas and recovering fluorine derivatized carbon nanotubes, then reacting fluorine derivatized carbon nanotubes with a nucleophile. Some of the fluorine substituents are replaced by nucleophilic substitution. If desired, the remaining fluorine can be completely or partially eliminated to produce single wall carbon nanotubes having substituents attached to the side wall of the nanotube. The substituents will, of course, be dependent on the nucleophile, and preferred nucleophiles include alkyl lithium species such as methyl lithium. Alternatively, fluorine may be fully or partially removed from fluorine derivatized carbon nanotubes by reacting the fluorine derivatized carbon nanotubes with various amounts of hydrazine, substituted hydrazine or alkyl amine. The present invention also provides seed materials for growth of single wall carbon nanotubes comprising a plurality of single wall carbon nanotubes or short tubular molecules having a catalyst precursor moiety covalently bound or physisorbed on the outer surface of the sidewall to provide the optimum metal cluster size under conditions that result in migration of the metal moiety to the tube end.

PRIORITY BENEFIT AND CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 09/787,473 “CHEMICAL DERIVATIZATION OF SINGLE-WALL CARBONNANOTUBES TO FACILITATE SOLVATION THEREOF; AND USE OF DERIVATIZEDNANOTUBES TO FORM CATALYST-CONTAINING SEED MATERIALS FOR USE IN MAKINGCARBON FIBERS” to Margraves et al., filed concurrent to the date of thisapplication. this application claims priority benefits to U.S. patentapplication Ser. No. 09/787,473, and which is a 371 of InternationalApplication No. PCT/US 99/21366, filed Sep. 17, 1999, which applicationclaims priority benefits to United States Patent Application Nos. (1)No. 60/101,092, filed Sep. 18, 1998; (2) No. 60/106,918 filed Nov. 3,1998; and (3) No. 60/138,505, filed Jun. 10, 1999, all of which arehereby incorporated by reference.

The present invention is related to the following corresponding U.S.patent applications, all of which are divisionals of the U.S. patentapplication Ser. No. 09/787,473:

Ser. No. 09/810,390 “CHEMICAL DERIVATIZATION OF SINGLE-WALL CARBONNANOTUBES TO FACILITATE SOLVATION THEREOF; AND USE OF DERIVATIZEDNANOTUBES TO FORM CATALYST-CONTAINING SEED MATERIALS FOR USE IN MAKINGCARBON FIBERS” to Margraves et al., filed concurrent to the date of thisapplication;

Ser. No. 09/809,885 “CHEMICAL DERIVATIZATION OF SINGLE-WALL CARBONNANOTUBES TO FACILITATE SOLVATION THEREOF; AND USE OF DERIVATIZEDNANOTUBES TO FORM CATALYST-CONTAINING SEED MATERIALS FOR USE IN MAKINGCARBON FIBERS” to Margraves et al., filed concurrent to the date of thisapplication;

Ser. No. 09/809,865 “CHEMICAL DERIVATIZATION OF SINGLE-WALL CARBONNANOTUBES TO FACILITATE SOLVATION THEREOF; AND USE OF DERIVATIZEDNANOTUBES TO FORM CATALYST-CONTAINING SEED MATERIALS FOR USE IN MAKINGCARBON FIBERS” to Margraves et al., filed concurrent to the date of thisapplication; and

Ser. No. 09/810,150 “CHEMICAL DERIVATIZATION OF SINGLE-WALL CARBONNANOTUBES TO FACILITATE SOLVATION THEREOF; AND USE OF DERIVATIZEDNANOTUBES TO FORM CATALYST-CONTAINING SEED MATERIALS FOR USE IN MAKINGCARBON FIBERS” to Margraves et al., filed concurrent to the date of thisapplication.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is directed to making chemical derivatives of carbonnanotubes and to uses for the derivatized nanotubes, including makingarrays as a basis for synthesis of carbon fibers.

2. Related Art

Fullerenes are closed-cage molecules composed entirely of sp²-hybridizedcarbons, arranged in hexagons and pentagons. Fullerenes (e.g., C₆₀) werefirst identified as closed spheroidal cages produced by condensationfrom vaporized carbon.

Fullerene tubes are produced in carbon deposits on the cathode in carbonarc methods of producing spheroidal fullerenes from vaporized carbon.Ebbesen et al. (Ebbesen I), “Large-Scale Synthesis Of Carbon Nanotubes,”Nature, Vol. 358, p. 220 (Jul. 16, 1992) and Ebbesen et al., (EbbesenII), “Carbon Nanotubes,” Annual Review of Materials Science, Vol. 24, p.235 (1994). Such tubes are referred to herein as carbon nanotubes. Manyof the carbon nanotubes made by these processes were multi-wallnanotubes, i.e., the carbon nanotubes resembled concentric cylinders.Carbon nanotubes having up to seven walls have been described in theprior art. Ebbesen II; Iijima et al., “Helical Microtubules Of GraphiticCarbon,” Nature, Vol. 354, p. 56 (Nov. 7, 1991).

Production of Single-Wall Nanotubes

Single-wall carbon nanotubes (SWNT) have been made in a DC arc dischargeapparatus of the type used in fullerene production by simultaneouslyevaporating carbon and a small percentage of VIII B transition metalfrom the anode of the arc discharge apparatus. See Iijima et al.,“Single-Shell Carbon Nanotubes of 1 nm Diameter,” Nature, Vol. 363, p.603 (1993); Bethune et al., “Cobalt Catalyzed Growth of Carbon Nanotubeswith Single Atomic Layer Walls,” Nature, Vol. 63, p. 605 (1993); Ajayanet al., “Growth Morphologies During Cobalt Catalyzed Single-Shell CarbonNanotube Synthesis,” Chem. Phys. Lett., Vol. 215, p. 509 (1993); Zhou etal., “Single-Walled Carbon Nanotubes Growing Radially From YC₂Particles,” Appl. Phys. Lett., Vol. 65, p. 1593 (1994); Seraphin et al.,“Single-Walled Tubes and Encapsulation of Nanocrystals Into CarbonClusters,” Electrochem. Soc., Vol. 142, p. 290 (1995); Saito et al.,“Carbon Nanocapsules Encaging Metals and Carbides,” J. Phys. Chem.Solids, Vol. 54, p. 1849 (1993); Saito et al., “Extrusion of Single-WallCarbon Nanotubes Via Formation of Small Particles Condensed Near anEvaporation Source,” Chem. Phys. Lett., Vol. 236, p. 419 (1995). It isalso known that the use of mixtures of such transition metals cansignificantly enhance the yield of single-wall carbon nanotubes in thearc discharge apparatus. See Lambert et al., “Improving ConditionsToward Isolating Single-Shell Carbon Nanotubes,” Chem. Phys. Lett., Vol.226, p. 364 (1994). While the arc discharge process can producesingle-wall nanotubes, the yield of nanotubes is low and the tubesexhibit significant variations in structure and size between individualtubes in the mixture. Individual carbon nanotubes are difficult toseparate from the other reaction products and purify.

An improved method of producing single-wall nanotubes is described inU.S. Ser. No. 08/687,665, entitled “Ropes of Single-Walled CarbonNanotubes” incorporated herein by reference in its entirety. This methoduses, inter alia, laser vaporization of a graphite substrate doped withtransition metal atoms, preferably nickel, cobalt, or a mixture thereof,to produce single-wall carbon nanotubes in yields of at least 50% of thecondensed carbon. The single-wall nanotubes produced by this method tendto be formed in clusters, termed “ropes,” of 10 to 1000 single-wallcarbon nanotubes in parallel alignment, held together by van der Waalsforces in a closely packed triangular lattice. Nanotubes produced bythis method vary in structure, although one structure tends topredominate.

A method of producing carbon fibers from single-wall carbon nanotubes isdescribed in PCT Patent Application No. PCT/US98/04513, incorporatedherein by reference in its entirety. The carbon fibers are producedusing SWNT molecules in a substantially two-dimensional array made up ofsingle-walled nanotubes aggregated (e.g., by van der Waals forces) insubstantially parallel orientation to form a monolayer extending indirections substantially perpendicular to the orientation of theindividual nanotubes. In this process the seed array tubes are opened atthe top (free) end and a catalyst cluster is deposited at this free end.A gaseous carbon source is then provided to grow the nanotube assemblyinto a fiber. In various processes involving metal cluster catalysis, itis important to provide the proper number of metal atoms to give theoptimum size cluster for single wall nanotube formation.

Derivatization of Single-Wall Nanotubes

Since the discovery of single wall carbon nanotubes (SWNTs) in 1993(Iijima, S. and Ichihashi, T., Nature 1993,363:603-605), researchershave been searching for ways to manipulate them chemically. While therehave been many reports and review articles on the production andphysical properties of carbon nanotubes, reports on chemicalmanipulation of nanotubes have been slow to emerge. There have beenreports of functionalizing nanotube ends with carboxylic groups (Rao, etal., Chem. Commun., 1996,1525-1526; Wong, et al., Nature,1998,394:52-55), and then further manipulation to tether them to goldparticles via thiol linkages (Liu, et al., Science, 1998,280:1253-1256). Haddon and co-workers (Chen, et al., Science, 1998,282:95-98) have reported solvating SWNTs by adding octadecylamine groupson the ends of the tubes and then adding dichlorocarbenes to thenanotube side wall, albeit in relatively low quantities (˜2%). Whiletheoretical results have suggested that functionalization of thenanotube side-wall is possible (Cahill, et al., Tetrahedron, 1996, 52(14):5247-5256), experimental evidence confirming this theory has notbeen obtained.

SUMMARY OF THE INVENTION

Accordingly, it is an object of this invention to provide a method forderivatizing carbon nanotubes, especially the side walls of single-wallcarbon nanotubes.

It is another object of this invention to provide a high yield, singlestep method for producing large quantities of continuous macroscopiccarbon fiber from single-wall carbon nanotubes using inexpensive carbonfeedstocks at moderate temperatures.

It is yet another object of this invention to provide macroscopic carbonfiber made by such a method. These and other objects of this inventionare met by one or more of the following embodiments.

This invention provides single wall carbon nanotubes and/or tubularcarbon molecules derivatized with substituents covalently bonded tocarbon atoms of the side wall of the nanotube or molecule. Thesubstituents may in principle be attached on the interior and/orexterior of the nanotube side wall, but the attachment will not bepredominantly on the exterior wall. In particular, the single wallcarbon nanotubes may have substituents selected from fluorine, alkyl andphenyl attached to the side wall. Such single wall carbon nanotubeshaving fluorine covalently bonded to the side wall of the nanotubedemonstrate high electrical resistance.

This invention also provides a method for derivatizing carbon nanotubescomprising reacting carbon nanotubes with fluorine gas, the fluorine gaspreferably being free of HF. Where the carbon nanotubes are single wallnanotubes, and the temperature is at least 500° C., the product may bemultiple wall carbon nanotubes derivatized with fluorine. Where thecarbon nanotubes are single wall nanotubes, and the temperature isbetween 250° C. and 500° C., the product is single wall carbon nanotubeshaving fluorine covalently bonded to carbon atoms of the side wall ofthe nanotube.

In one embodiment, this invention also provides a method for preparingsingle wall carbon nanotubes having substituents attached to the sidewall of the nanotube by reacting single wall carbon nanotubes withfluorine gas and recovering fluorine derivatized carbon nanotubes, thenreacting fluorine derivatized carbon nanotubes with a nucleophile. Someof the fluorine substituents are replaced by nucleophilic substitution.If desired, the remaining fluorine can be completely or partiallyeliminated to produce single wall carbon nanotubes having substituentsattached to the side wall of the nanotube. The substituents will, ofcourse, be dependent on the nucleophile, and preferred nucleophilesinclude alkyl lithium species such as methyl lithium. Alternatively,fluorine may be fully or partially removed from fluorine derivatizedcarbon nanotubes by reacting the fluorine derivatized carbon nanotubeswith various amounts of hydrazine, substituted hydrazine or alkyl amine.

This invention also provides a process for preparing a suspension orsolution of single wall carbon nanotubes in various solvents from whichindividual single wall carbon nanotubes may be isolated, the processcomprising providing a mass of single wall carbon nanotubes that includebundles of fibers held in close association by van der Waals forces,derivatizing the side walls of the single wall carbon nanotubes with aplurality of chemical moieties distributed substantially uniformly alongthe length of said single wall carbon nanotube side walls, said chemicalmoieties having chemical and steric properties sufficient to prevent thereassembly of van der Waals force bound bundles, producing truesolutions and recovering the individual, derivatized single wall carbonnanotubes from said solution or suspension. Preferably, the attachedchemical moieties are fluorine to provide solution in various alcohols,preferably isopropyl alcohol, and various R-groups to appropriate toprovide solubility in other solvents including CHCl₃, Dimethylformamide,etc.

In another embodiment, a method for forming a macroscopic moleculararray of tubular carbon molecules is disclosed. This method includes thesteps of providing at least about 10⁶ tubular carbon molecules ofsubstantially similar length in the range of 50 to 500 nm; introducing alinking moiety onto at least one end of the tubular carbon molecules;providing a substrate coated with a material to which the linking moietywill attach; and contacting the tubular carbon molecules containing alinking moiety with the substrate.

The present invention also provides seed materials for growth of singlewall carbon nanotubes comprising a plurality of single wall carbonnanotubes or short tubular molecules having a catalyst precursor moietycovalently bound or physisorbed on the outer surface of the sidewall toprovide the optimum metal cluster size under conditions that result inmigration of the metal moiety to the tube end.

This invention also provides a seed array for the catalytic productionof assemblies of single wall carbon nanotubes comprising a plurality ofrelatively short single wall carbon nanotubes assembled in a generallyparallel configuration, and disposed on the side wall of each saidsingle wall carbon nanotube a sufficient quantity of physisorbed orcovalently bonded transition metal catalyst precursor moieties toprovide active catalyst metal atom clusters of the proper size to growsingle wall carbon nanotubes under conditions that promote thegeneration of metal atoms and the migration of said metal atoms to thefree ends of said single wall carbon nanotubes.

In another embodiment, a method for continuously growing a macroscopiccarbon fiber comprising at least about 10⁶ single-wall nanotubes ingenerally parallel orientation is disclosed. In this method, amacroscopic molecular array of at least about 10⁶ tubular carbonmolecules in generally parallel orientation is provided. The array isprocessed to provide a single plane of open-ended nanotubes at an anglegenerally perpendicular to the axes of parallel tubes in the array. Theopen ends of the tubular carbon molecules in the array are thencontacted with a catalytic metal by causing migration of metal atomsreleased from side wall attached catalyst precursor groups. A gaseoussource of carbon is supplied to the end of the array while localizedenergy is applied to the end of the array in order to heat the end to atemperature in the range of about 500° C. to about 1300° C. The growingcarbon fiber is continuously recovered.

In another embodiment, an apparatus for forming a continuous macroscopiccarbon fiber from a macroscopic molecular template array similar to thatdescribed above, comprising at least about 10⁶ single-wall carbonnanotubes having a catalytic metal deposited on the open ends of saidnanotubes is disclosed. This apparatus includes a means for locallyheating only the open ends of the nanotubes in the template array in agrowth and annealing zone to a temperature in the range of about 500° C.to about 1300° C. It also includes a means for supplying acarbon-containing feedstock gas to the growth and annealing zoneimmediately adjacent the heated open ends of the nanotubes in thetemplate array. It also includes a means for continuously removinggrowing carbon fiber from the growth and annealing zone whilemaintaining the growing open end of the fiber in the growth andannealing zone.

The foregoing objectives, and others apparent to those skilled in theart, are achieved according to the present invention as described andclaimed herein, and in the text of U.S. provisional application Ser. No.60/106,918, filed Nov. 3, 1998, which is incorporated herein in itsentirety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. A) TEM image of pure, unreacted SWNT B) TEM of SWNT after beingfluorinated at 325° C. C) TEM of SWNT after being fluorinated at 500° C.D) another TEM of SWNT fluorinated at 500° C. showing the formation ofMWNT.

FIG. 2. Raman spectrum of pure, unreacted carbon SWNT.

FIG. 3. Raman spectra of SWNT fluorinated at A) 250° C. B) 325° C. andC) 400° C.

FIG. 4. Raman spectra showing the defluorination of the nanotubesoriginally fluorinated at A) 250° C. B) 325° C. and C) 400° C.

FIG. 5. A) SEM of pure, unreacted SWNT B) SEM of SWNT after having beenfluorinated at 325° C. for 5 hours C) SEM of SWNT fluorinated at 325° C.and then defluorinated in hydrazine.

FIG. 6. A) Raman spectrum of SWNT after being fluorinated and thenmethylated. B) Raman spectrum of the pyrolyzed methylated. SWNT whichlooks exactly like the Raman spectrum of untreated, SWNT.

FIG. 7. B) EI mass spectrum of products given off during the pyrolysisof methylated SWNT. This spectrum corresponds to a probe temperature of˜400° C.

FIG. 8. A) Infrared spectrum of the product of a 3 hour methylationreaction B) Infrared spectrum, of the product of a 12 hour methylationreaction.

FIG. 9 shows a SEM image of purified SWNTs.

FIG. 10A shows an AFM image of fluorotubes which have been. dissolved in2-butanol and dispersed on inica.

FIG. 10B shows a typical height analysis of the scan in FIG. 2A,revealing the tube diameters to be on the order of 1.2-1.4 nm, values onthe order of those determined previously for this product using TEM andXRD.

FIG. 11 shows a UV spectrum of fluorotubes solvated in 2-propanol aftersonication times of A) 10 min. B) 40 min. and C 130 min.

FIG. 12A shows an AFM image of fluorotubes after having beendefluorinated with N₂H₄, filtered, resuspended in DMF and dispersed onmica.

FIG. 12B shows an AFM image of untreated SWNTs dispersed on mica.

FIG. 13A shows a Raman spectrum of pure, untreated SWNTs.

FIG. 13B shows a Raman spectrum of fluorotubes.

FIG. 13C shows a Raman spectrum of fluorotubes after having beendefluorinated with N₂H₄. *denotes Ar plasma line.

FIG. 14 is a schematic representation of a portion of an homogeneousSWNT molecular array according to the present invention.

FIG. 15 is a schematic representation of an heterogeneous SWNT moleculararray according to the present invention.

FIG. 16 is a schematic representation of the growth chamber of the fiberapparatus according to the present invention.

FIG. 17 is a schematic representation of the pressure equalization andcollection zone of the fiber apparatus according to the presentinvention.

FIG. 18 is a composite array according to the present invention.

FIG. 19 is a composite array according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Carbon has from its very essence not only the propensity toself-assemble from a high temperature vapor to form perfect spheroidalclosed cages (of which C₆₀ is prototypical), but also (with the aid of atransition metal catalyst) to assemble into perfect single-wallcylindrical tubes which may be sealed perfectly at both ends with asemifullerene dome. These tubes, which may be thought of asone-dimensional single crystals of carbon, are true fullerene molecules.

Single-wall carbon nanotubes are much more likely to be free of defectsthan multi-wall carbon nanotubes. Defects in single-wall carbonnanotubes are less likely than defects in multi-walled carbon nanotubesbecause the latter have neighboring walls that provide for easily-formeddefect sites via bridges between unsaturated carbon valances in adjacenttube walls. Since single-wall carbon nanotubes have fewer defects, theyare stronger, more conductive, and therefore more useful than multi-wallcarbon nanotubes of similar diameter.

Carbon nanotubes, and in particular the single-wall carbon nanotubes,are useful for making electrical connectors in micro devices such asintegrated circuits or in semiconductor chips used in computers becauseof the electrical conductivity and small size of the carbon nanotube.The carbon nanotubes are useful as antennas at optical frequencies, andas probes for scanning probe microscopy such as are used in scanningtunneling microscopes (STM) and atomic force microscopes (AFM). Thecarbon nanotubes may be used in place of or in conjunction with carbonblack in tires for motor vehicles. The carbon nanotubes are also usefulas supports for catalysts used in industrial and chemical processes suchas hydrogenation, reforming and cracking catalysts.

Ropes of single-wall carbon nanotubes will conduct electrical chargeswith a relatively low resistance. Ropes are useful in any applicationwhere an electrical conductor is needed, for example as an additive inelectrically conductive paints or in polymer coatings or as the probingtip of an STM.

In defining carbon nanotubes, it is helpful to use a recognized systemof nomenclature. In this application, the carbon nanotube nomenclaturedescribed by M. S. Dresselhaus, G. Dresselhaus, and P. C. Eklund,Science of Fullerness and Carbon Nanotubes, Chap. 19, especially pp.756-760, (1996), published by Academic Press, 525 B Street, Suite 1900,San Diego, Calif. 92101-4495 or 6277 Sea Harbor Drive, Orlando, Fla.32877 (ISBN 0-12-221820-5), which is hereby incorporated by reference,will be used. The single wall tubular fullerenes are distinguished fromeach other by double index (n,m) where n and m are integers thatdescribe how to cut a single strip of hexagonal “chicken-wire” graphiteso that it makes the tube perfectly when it is wrapped onto the surfaceof a cylinder and the edges are sealed together. When the two indicesare the same, m=n, the resultant tube is said to be of the “arm-chair”(or n,n) type, since when the tube is cut perpendicular to the tubeaxis, only the sides of the hexagons are exposed and their patternaround the periphery of the tube edge resembles the arm and seat of anarm chair repeated n times. Arm-chair tubes are a preferred form ofsingle-wall carbon nanotubes since they are metallic, and have extremelyhigh electrical and thermal conductivity. In addition, all single-wallnanotubes have extremely high tensile strength.

Carbon nanotubes may have diameters ranging from about 0.6 nanometers(nm) for a single-wall carbon nanotube up to 3 nm, 5 nm, 10 nm, 30 nm,60 nm or 100 nm for single-wall or multi-wall carbon nanotubes. Thecarbon nanotubes may range in length from 50 nm up to 1 millimeter (mm),1 centimeter (cm), 3 cm, 5 cm, or greater. The yield of single-wallcarbon nanotubes in the product made by this invention is unusuallyhigh.

Catalytic Formation of Carbon Nanotubes

As will be described further, one or more transition metals of Group VIBchromium (Cr), molybdenum (Mo), tungsten (W) or Group VIII B transitionmetals, e.g., iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru),rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) and platinum(Pt) catalyze the growth of a carbon nanotube and/or ropes whencontacted with a carbon bearing gas such carbon monoxide andhydrocarbons, including aromatic hydrocarbons, e.g., benzene, toluene,xylene, cumene, ethylbenzene, naphthalene, phenanthrene, anthracene ormixtures thereof, non-aromic hydrocarbons, e.g., methane, ethane,propane, ethylene, propylene, acetylene or mixtures thereof; andoxygen-containing hydrocarbons, e.g., formaldehyde, acetaldehyde,acetone, methanol, ethanol or mixtures thereof. Mixtures of one or moreGroup VIB or VIIIB transition metals also selectively producesingle-wall carbon nanotubes and ropes of single-wall carbon nanotubesin higher yields. The mechanism by which the growth in the carbonnanotube and/or rope is accomplished is not completely understood.However, it appears that the presence of the one or more Group VI B orVIII B transition metals on the end of the carbon nanotube facilitatesthe addition of carbon from the carbon vapor to the solid structure thatforms the carbon nanotube. Applicants believe this mechanism isresponsible for the high yield and selectivity of single-wall carbonnanotubes and/or ropes in the product and will describe the inventionutilizing this mechanism as merely an explanation of the results of theinvention. Even if the mechanism is proved partially or whollyincorrect, the invention which achieves these results is still fullydescribed herein.

One aspect of the invention comprises a method of making carbonnanotubes and/or ropes of carbon nanotubes which comprises supplyingcarbon vapor to the live end of one or more of a carbon nanotubesgrowing by a catalytic process in which there is a “live end” of thenanotube in contact with a nanometer-scale transition metal particlethat serves as a catalyst. The live end of the nanotube is maintained incontact with a carbon bearing feedstock gas in an annealing zone at anelevated temperature. In one process of this type carbon in vapor formmay be supplied in accordance with this invention by an apparatus inwhich a laser beam impinges on a target comprising carbon that ismaintained in a heated zone. A similar apparatus has been described inthe literature, for example, in U.S. Pat. No. 5,300,203, or inPCT/US96/14188, both of which are incorporated herein by reference, andin Chai, et al., “Fullerenes with Metals Inside,” J. Phys. Chem., vol.95, no. 20, p. 7564 (1991). Alternatively carbon may be added to thelive end by the direct action of the catalytic particle in the annealingzone with a carbon-bearing feedstock gas such as carbon monoxide andhydrocarbons, including aromatic hydrocarbons, e.g., benzene, toluene,xylene, cumene, ethylbenzene, naphthalene, phenanthrene, anthracene ormixtures thereof, non-aromic hydrocarbons, e.g., methane, ethane,propane, ethylene, propylene, acetylene or mixtures thereof; andoxygen-containing hydrocarbons, e.g., formaldehyde, acetaldehyde,acetone, methanol, ethanol or mixtures thereof.

According to this invention, a “live end” can also be produced on acarbon nanotube derivatized with chemical moieties which bind Group VI Bor Group VIII B metal to the tube. This mode is discussed in greaterdetail below. Additional carbon vapor is then supplied to the live endof a carbon nanotube under the appropriate conditions to increase thelength of the carbon nanotube.

The carbon nanotube that is formed is not always a single-wall carbonnanotube; it may be a multi-wall carbon nanotube having two, five, tenor any greater number of walls (concentric carbon nanotubes).Preferably, though, the carbon nanotube is a single-wall carbonnanotube, and this invention provides a way of selectively producingsingle-wall carbon nanotubes in greater and sometimes far greaterabundance than multi-wall carbon nanotubes.

Elongation of Single-Wall Nanotubes

As contemplated by this invention, growth or elongation of single-wallcarbon nanotubes requires that carbon in vapor form be supplied to thelive end of the growing nanotube in an annealing zone. In thisapplication, the term “live end” of a carbon nanotube refers to the endof the carbon nanotube on which catalytic amounts of one or more GroupVI B or VIII B transition metals are located. The catalyst should bepresent on the open SWNT ends as a metal cluster containing from about10 metal atoms up to about 200 metal atoms (depending on the SWNTmolecule diameter). Preferred are metal clusters having a cross-sectionequal to from about 0.5 to about 1.0 times the tube diameter (e.g.,about 0.7 to 1.5 nm).

A carbon nanotube having a live end will grow in length by the catalyticaddition of carbon from the vapor to the live end of the carbon nanotubeif the live end is placed in an annealing zone and then additionalcarbon-containing vapor is supplied to the live end of the carbonnanotube. The annealing zone where the live end of the carbon nanotubeis initially formed should be maintained at a temperature of 500° to1500° C., more preferably 1000° to 1400° C. and most preferably 1100 to1300° C. In embodiments of this invention where carbon nanotubes havinglive ends are caught and maintained in an annealing zone and grown inlength by further addition of carbon (without the necessity of addingfurther Group VI B or VIII B transition metal vapor), the annealing zonemay be cooler, 400° to 1500° C., preferably 400° to 1200° C., mostpreferably 500° to 700° C. The pressure in the annealing zone should bemaintained in the range of pressure appropriate to thecatalyst/feedstock system being used, i.e., 50 to 2000 Torr., morepreferably 100 to 800 Torr, and most preferably 300 to 600 Torr in thecase of carbon or hydrocarbon gasses, but up to 100 atmospheres in thecase of CO feedstock. The atmosphere in the annealing zone will containcarbon in some form. Normally, the atmosphere in the annealing zone willalso comprise a gas that sweeps the carbon vapor through the annealingzone to a collection zone. Any gas that does not prevent the formationof carbon nanotubes will work as the sweep gas, but preferably the sweepgas is an inert gas such as helium, neon, argon, krypton, xenon, ormixtures of two or more of these. Helium and Argon are most preferred.The use of a flowing inert gas provides the ability to controltemperature, and more importantly, provides the ability to transportcarbon to the live end of the carbon nanotube. In some embodiments ofthe invention, when other materials are being vaporized along withcarbon, for example one or more Group VI B or VIII B transition metals,those compounds and vapors of those compounds will also be present inthe atmosphere of the annealing zone. If a pure metal is used, theresulting vapor will comprise the metal. If a metal oxide is used, theresulting vapor will comprise the metal and ions or molecules of oxygen.

It is important to avoid the presence of too many materials that kill orsignificantly decrease the catalytic activity of the one or more GroupVI B or VIII B transition metals at the live end of the carbon nanotube.It is known that the presence of too much water (H₂O) and/or oxygen (O₂)will kill or significantly decrease the catalytic activity of the one ormore Group VI B or VIII B transition metals. Therefore, water and oxygenare preferably excluded from the atmosphere in the annealing zone.Ordinarily, the use of a sweep gas having less than 5 wt %, morepreferably less than 1 wt % water and oxygen will be sufficient. Mostpreferably the water and oxygen will be less than 0.1 wt %.

The carbon-containing vapor supplied to the live end in the annealingzone may be provided by evaporation of a solid carbon target usingenergy supplied by an electric arc or laser, as described herein.However, once the single-wall carbon nanotube having a live end isformed, the live end will catalyze growth of the single-wall carbonnanotube at lower temperatures and with other carbon sources. Analternative carbon source for growing the SWNT may be fullerenes, thatcan be transported to the live end by the flowing sweep gas. The carbonsource can be graphite particles carried to the live end by the sweepgas. The carbon source can be a hydrocarbon that is carried to the liveend by a sweep gas or a hydrocarbon gas or mixture of hydrocarbon gassesintroduced into the annealing zone. Hydrocarbons useful include methane,ethane, propane, butane, ethylene, propylene, benzene, toluene or anyother paraffinic, olefinic, cyclic or aromatic hydrocarbon, or any otherhydrocarbon. Another alternative that may be used as a source ofcarbon-containing vapor are other gaseous compounds that can formelemental carbon by disproportionation such as CO, C₂F₄ and C₂H₄.

Chemically Modified Carbon Nanotubes

The present invention provides carbon nanotubes having chemicallyderivatized side walls. In preferred embodiments, the derivatizationfacilitates formation of more complex functional compounds with carbonnanotubes. Derivatization also enables complexing of Group VI B and/orGroup VIII B metals on the nanotubes. In particularly preferredembodiments, the derivatized nanotubes are derivatized molecular growthprecursors of this invention which may have the following structures andfunctions:

where

M is a group VI B or VIII B metal;

n is a number from 10-100000, preferably 50 to 20000; and

R is a linking or complexing moiety that can include groups selectedfrom the group consisting of alkyl, acyl, aryl, aralkyl, halogen;substituted or unsubstituted thiol; unsubstituted or substituted amino;hydroxy, and OR′ wherein R′ is selected from the group consisting ofhydrogen, alkyl, acyl, aryl aralkyl, unsubstituted or substituted amino;substituted or unsubstituted thiol; and halogen; and a linear or cycliccarbon chain optionally interrupted with one or more heteroatom, andoptionally substituted with one or more ═O, or ═S, hydroxy, anaminoalkyl group, an amino acid, or a peptide of 2-8 amino acids.

Other embodiments of the derivatized nanotubes of this invention havestructures as described above, except metal is not present and the Rgroup does not necessarily serve to form complexes. The followingdefinitions are used herein.

The term “alkyl” as employed herein includes both straight and branchedchain radicals, for example methyl, ethyl, propyl, isopropyl, butyl,t-butyl, isobutyl, pentyl, hexyl, isohexyl, heptyl, 4,4-dimethylpentyl,octyl, 2,2,4-trimethylpentyl, nonyl, decyl, undecyl, dodecyl, thevarious branched chain isomers thereof The chain may be linear orcyclic, saturated or unsaturated, containing, for example, double andtriple bonds. The alkyl chain may be interrupted or substituted with,for example, one or more halogen, oxygen, hydroxy, silyl, amino, orother acceptable substituents.

The term “acyl” as used herein refers to carbonyl groups of the formula—COR wherein R may be any suitable substituent such as, for example,alkyl, aryl, aralkyl, halogen; substituted or unsubstituted thiol;unsubstituted or substituted amino, unsubstituted or substituted oxygen,hydroxy, or hydrogen.

The term “aryl” as employed herein refers to monocyclic, bicyclic ortricyclic aromatic groups containing from 6 to 14 carbons in the ringportion, such as phenyl, naphthyl, substituted phenyl, or substitutednaphthyl, wherein the substituent on either the phenyl or naphthyl maybe for example C₁₋₄ alkyl, halogen, C₁₋₄ alkoxy, hydroxy or nitro.

The term “aralkyl” as used herein refers to alkyl groups as discussedabove having an aryl substituent, such as benzyl, p-nitrobenzyl,phenylethyl, diphenylmethyl, and triphenylmethyl.

The term “aromatic or non-aromatic ring” as used herein includes 5-8membered aromatic and non-aromatic rings uninterrupted or interruptedwith one or more heteroatom, for example O, S, SO, SO₂, and N, or thering may be unsubstituted or substituted with, for example, halogen,alkyl, acyl, hydroxy, aryl, and amino, said heteroatom and substituentmay also be substituted with, for example, alkyl, acyl, aryl, oraralkyl.

The term “linear or cyclic” when used herein includes, for example, alinear chain which may optionally be interrupted by an aromatic ornon-aromatic ring. Cyclic chain includes, for example, an aromatic ornon-aromatic ring which may be connected to, for example, a carbon chainwhich either precedes or follows the ring.

The term “substituted amino” as used herein refers to an amino which maybe substituted with one or more substituent, for example, alkyl, acyl,aryl, aralkyl, hydroxy, and hydrogen.

The term “substituted thiol” as used herein refers to a thiol which maybe substituted with one or more substituent, for example, alkyl, acyl,aryl, aralkyl, hydroxy, and hydrogen.

Typically, open ends may contain up to about 20 substituents and closedends may contain up to about 30 substituents. It is preferred, due tostearic hindrance, to employ up to about 12 substituents per end.

In addition to the above described external derivatization, the SWNTmolecules of the present invention can be modified endohedrally, i.e.,by including one or more other atoms or molecules inside the structure,as is known in the endohedral fullerene art.

To produce endohedral tubular carbon molecules, the internal species(e., metal atom) can either be introduced during the SWNT formationprocess or added after preparation of the nanotubes.

Endohedrally loaded tubular carbon molecules can then be separated fromempty tubes and any remaining loading materials by taking advantage ofthe new properties introduced into the loaded tubular molecules, forexample, where the metal atom imparts magnetic or paramagneticproperties to the tubes, or the bucky ball imparts extra mass to thetubes. Separation and purification methods based on these properties andothers will be readily apparent to those skilled in the art.

Derivatization of SWNT Sidewalls With Fluorine

Since the discovery of single wall carbon nanotubes (SWNT) Iijima, etal. (1993), there has been a flurry of research activity aimed atunderstanding their physical properties (Issi, et al. (1995), Carbon,33:941-948), elucidating their growth mechanisms (Cornwell, et al.(1997), Chem. Phys. Lett., 278:262-266), and developing novel uses forthem (Dillon, et al. (1997), Nature, 386:377-389). Chemistry involvingSWNT is still in its infancy. This is due, in large part, to previousdifficulties in obtaining reasonable quantities of highly purified SWNT.

Progress in the bulk synthesis and purification (Rinzler, et al., 1998,App. Phys. A, 67:29-37) of SWNT is now making available high qualitysamples in sufficient quantities to begin exploring the chemicalmodification of this fascinating class of materials. Recently,sono-chemistry was employed to cut the long, intertangled tubes intoindependent, macro-molecular scale, open tube fragments (50-300 nm long)(Liu, et al., 1998). In that work, the high reactivity of the-danglingcarbon bonds at the open tube ends was exploited to tether the tubes togold particles via thiol linkages.

In contrast to the open tube ends, the side-walls of the SWNT, by virtueof their aromatic nature, possess a chemical stability akin to that ofthe basal plane of graphite (Aihara, 1994, J. Phys. Chem.,98:9773-9776). The chemistry available for modification of the nanotubeside-wall (without disruption of the tubular structure) is thussignificantly more restrictive. However, the present inventors haveadapted technology developed in the fluorination of graphite (see, eg.,Lagow, et al., 1974, J. Chem. Soc., Dalton Trans., 12:1268-1273) to thechemical manipulation of the SWNT side-wall by fluorinating high puritySWNT and then defluorinating them. Once fluorinated, single-wall carbonnanotubes can serve a staging point for a wide variety of side-wallchemical functionalizations, in a manner similar to that observed forfluorinated fullerenes (see Taylor, et al., 1992, J. Chem. Soc., Chem.Comm., 9:665-667, incorporated herein by reference).

According to the present invention, single-wall carbon nanotubes arederivatized by exposure to a fluorinating agent, which may be fluorinegas or any other well known fluorinating agent such as XeF₂, XeF₄, ClF₃,BrF₃, or IF₅. XeF₂, and XeF₄ may be advantageous, being free of HF.Alternatively, solid fluorinating agents, such as AgF₂ or MnF₃, may bereacted in slurry with SWNT.

Purified single wall carbon nanotubes (SWNT) were fluorinated by theinventors by treatment with F₂ at several different temperatures andconcentrations using various mixtures of about 5% F₂ in a one-atmospherepressure mixture with rare gases, including He and Ar. The reactortemperature was between 150° C. and 400° C. Infrared spectroscopy wasused to verify the existence of covalent carbon-fluorine bonds. Productstoichiometries were determined and transmission electron microscopy(TEM) was used to verify whether or not the fluorination was destructiveof the tubes. SWNT fluorinated at three different temperatures were thendefluorinated using hydrazine. Raman spectroscopy was used to verifywhether or not the products of the defluorination were in fact SWNT. Itwas determined, via scanning electron microscopy (SEM) and two-pointresistance measurements, that the bulk of the SWNT survive thefluorination process at temperatures up to 325° C. and that the fluorinecan be effectively removed from the tubes with hydrazine to regeneratethe unfluorinated starting material.

Not unexpectedly, the electronic properties of the fluorinated tubesdiffer dramatically from those of their unfluorinated counterparts.While the untreated SWNT are good conductors (10-15 Ω two proberesistance across the length of the ˜10×3 mm×30 μm bucky paper samples),the tubes fluorinated at temperatures of 250° C. and above areinsulators (two probe resistance >20 MΩ).

Gravimetric and electron microprobe analysis demonstrated that largeamounts of fluorine can be added to SWNT. Resistance measurements alongwith vibrational spectroscopy (Raman, IR) confirm the formation of newchemical bonds to the nanotube superstructure. Contributions of absorbedmolecular fluorine to the overall fluorine uptake are precluded at thesetemperatures (Watanabe, et al., 1988). It may be concluded, therefore,that fluorine is being covalently attached to the side wall of the SWNT.

TEM studies have shown that at fluorination temperatures as high as 325°C., the majority of the fluorination product maintains a tube-likestructure. These studies also indicate that at 500° C., the single walltubular structure does not survive the fluorination process and thatsome MWNT-like structures are being formed.

From the product stoichiometries, resistance measurements and IR spectrait is clear that reaction temperatures in excess of 150° C. allow one tocovalently add significant amounts of fluorine to the tube wall. Thesmall amount of fluorine that does show up in the product of the 150° C.fluorination reaction could be attributed to a combination of absorbedfluorine and fluorination of the end caps of the SWNT.

Fluoride can also be effectively removed from the SWNT using anhydroushydrazine and that the rejuvenated product is in fact a SWNT. Theinventors have found that, once fluorinated, SWNT can be defluorinatedwith anhydrous hydrazine via the following reaction:CF_(n)+(n/4)N₂H₄→C+nHF+(n/4)N₂. From the results of these defluorinationexperiments and the Raman and SEM studies associated with them, itappears that a majority of the tubes are destroyed at fluorinationtemperatures of above 400° C., whereas only a slight amount of tubedestruction occurs at 250° C.

For reactions in which only the outside of the tube is being fluorinated(the SWNT used in this study were closed at the ends), there is alimiting stoichiometry of C₂F for which the fluorinated tube can stillmaintain its tube-like (albeit puckered) structure. This is supported bythe product stoichiometries obtained via elemental analysis and theevidence of significant tube destruction at fluorination temperaturesgreater than 325° C. Further addition of fluorine would then lead to thebreaking of carbon—carbon bonds and, hence, destruction of the tube.Accordingly, this invention provides a method of derivatizing SWNT withF₂ to add fluorine substituents to the exterior of the sidewalls instoichiometries of up to C₂F, although lesser amounts of fluorine canalso be attached by further diluting the fluorine or by lowering thereaction temperature.

Changing the Derivatization of SWNT by Fluorine Substitution

Because the inertness of the SWNT side wall approximates that of thebasal plane of graphite, chemistry involving the SWNT side wall may bequite limited. However, the present invention provides methods forfluorination of single wall carbon nanotubes (SWNT) where fluorine iscovalently bound to the side wall of the nanotube and thus provide sitesfor chemical reactions to occur. Functionalization via a fluorinatedprecursor may thus provide an attractive route to a wide range of sidewall derivatizations.

In a particular embodiment, highly purified single wall carbon nanotubes(SWNTs) may be fluorinated to form “fluorotubes” which can then besolvated as individual tubes. For example, fluorotubes may be solvatedin various alcohol solvents via ultrasonication. The solvation ofindividual fluorotubes has been verified by dispersing the solvatedtubes on a mica substrate and examining them with atomic forcemicroscopy (AFM). Elemental analysis of the tubes reveals that lightsonication in alcohol solvents does not remove significant amounts ofthe fluorine. These solutions will persist long enough (over a week) topermit solution phase chemistry to be carried out on the fluorotubes.For example, the solvated fluorotubes can be treated with hydrazine toremove fluorine, leading to precipitation from solution of normal,unfluorinated SWNTs. Alternatively, fluorotubes can be reacted withsodium methoxide to yield methoxylated SWNTs. These reaction productshave also been characterized by elemental analysis and a variety ofspectroscopies and microscopies.

The present inventors have, for the first time, functionalized thesidewalls of SWNTs by reacting them with elemental fluorine. Theinventors have discovered that fluorine could be added to the side wallof carbon nanotubes yielding stoichiometries up to approximately C₂Fwithout destruction of the tube-like structure. The inventors have alsodiscovered that a high degree of solvation can be achieved by sonicatingfluorinated SWNTs in a variety of alcohol solvents such as methanol,ethanol, and isopropanol. As demonstrated herein, reactions can becarried out on these nanotubes while in solution by reacting them withhydrazine which serves as a defluorinating agent. It has also beendemonstrated that these “fluorotubes” can be reacted with sodiummethoxide (a strong nucleophile) while in solution to form methoxylatedSWNTs.

The inventors have shown that single wall carbon nanotubes can befluorinated and then sonicated in alcohols to form stable solutions offluorotubes. This solvation allows one to manipulate the fluorotubes inways that were previously unavailable and opens the door to a widevariety of possibilities with respect to exploring the physical andchemical properties of fluorotubes. “Tuning” the fluorine content of afluorotube by first fluorinating it heterogeneously, solvating it in analcohol, and then defluorinating it with substoichiometric quantities ofhydrazine is consequently available as a way of making a wide varietyfluorotubes with differing fluorine contents and in some instances quitedifferent properties.

The inventors have further demonstrated that once solvated, thesefluorotubes can then be reacted with species while in solution to eitherdefluorinate or further functionalize them. The chemistry possible withthese solvated fluorotubes provides an important route to the synthesisof a wide variety of functionalized nanotubes having many different anduseful properties.

An exemplary derivatization is the methylation of SWNT. Methylated SWNTare the product of the nucleophilic substitution of fluorine (attachedto the SWNT side wall) by the methyl groups in methyl lithium.Nucleophilic substitution of this type has been previously reported forthe reaction between fluorinated C₆₀ and alkyl lithium species (Taylor,et al., 1992). The C—F bonds in fullerene cages and tubes are weakenedrelative to C—F bonds in alkyl fluorides by an eclipsing strain effect(Taylor, 1998 Russian Chem. Bull., 47:823-832). This renders the bondsmore susceptible to nucleophilic attack. A normal S_(N)2 process isgeometrically impossible and a S_(N)I process would be extremelyunlikely, so either a novel front side displacement or possibly anaddition-elimination process is responsible for the nucleophilicsubstitution (See Taylor, 1995, in “The Chemistry of Fullerenes,” R.Taylor, ed., world Scientific Publishing, London, pp.208-209).

EXAMPLES Example 1

1.1 Fluorination of Single-Wall Carbon Nanotubes

Single-walled carbon nanotubes were produced by the dual pulsed laservaporization of Co/Ni doped graphite rods and purified by techniquesdescribed previously (Rinzler, et al., 1998). The purification productis a metastable colloidal suspension of SWNT “ropes” (bundles ofhexagonally close packed tubes ranging from a few to 200 SWNT, SeeThess, et al., 1996) in a 0.2% aqueous solution of Triton X-100surfactant. Filtering the solution through a PTFE filter membrane andwashing with methanol to remove residual surfactant leaves a black filmon the surface. If this layer is sufficiently thick (10-75 μm) it can bepeeled off to form a free standing film or “bucky paper” of SWNT. Thisform has appreciable mechanical integrity and is convenient forhandling, and for electrical conductivity and Raman scatteringmeasurements. It is the fluorination of this “bucky paper” that isdescribed here.

In fluorinating the SWNT, elemental fluorine (Air Products, 98%) wasused as the fluorinating agent. HF, being the major impurity in thefluorine, was removed by passing it through an HF trap (Matheson GasProducts) containing sodium fluoride pellets. The fluorine, diluted withhelium (Trigas, 99.995%), was then passed through atemperature-controlled Monel flow reactor containing the SWNT sample.

Prior to fluorination, the purified “bucky paper” was vacuum baked at1100° C. (2×10⁶ Torr) for several hours in order to desorb any residualsurface contaminants. For each reaction a pre-weighed piece of “buckypaper (weighing 150-200 μg) was used. F₂ and He flow rates for eachreaction were 2 sccm and 20 sccm, respectively. In each case thereaction time was 5 hours. The only variable was reaction temperature.As the kinetics of inorganic carbon+fluorine reactions are highlytemperature dependent (Watanabe, et al., 1988, “Graphite fluorides,”Elsevier, Amsterdam), several reactions were carried out at thefollowing temperatures: 150° C., 250° C., 325° C., 400° C., 500° C. and600° C. At reaction temperatures of 325° C. and 400° C., thefluorination was begun at 250° C. and after one hour, the F₂ flow wasstopped and the reactor temperature brought up to the appropriate levelfor an additional 4 hours. For the reactions at 500° C. and 600° C., thesample was fluorinated for 1 hour at 250° C., 1 hour at 400° C. and then3 hours at the specified reaction temperature. The rationale behind this“stepped reaction temperature procedure” was to minimize, as much aspossible, the decomposition: CF₄, C₂F₄, C₂F₆, etc. which has been welldocumented in the fluorination of graphite (Kamarchik, et al., 1978,Acc. Chem. Res., 11:196-300) and fullerenes (Selig, et al., 1991, J. Am.Chem. Soc., 113:5475-5476).

Product stoichiometries as a function of reaction temperature wereobtained both gravimetrically (TA Instruments TGA-DTA 2960 microbalance)and via electron microprobe analysis (Carneca SX 50). Infaredspectroscopy (Perkin-Elmer Paragon 1000 FT-IR) was used to confirm thepresence of covalently bound fluorine. Transmission electron microscopy(JEOL model 2010 TEM using 100 keV beam energy) was used to determineif, and at what temperature the tubes were being destroyed (i.e.,unzipped”) by the fluorination. Raman spectroscopy (Jobin Yvon-Spexmodel HR460 monochrometer coupled with an ISA Spectrum ONE series CCDdetector and using a 532 nm Nd:YAG laser excitation source), scanningelectron microscopy (JEOL model JSM-6320F field emission SEM using 5 keVbeam energy) and two-point resistivity measurements were used to analyzethe untreated, fluorinated and defluorinated SWNT samples.

Infared spectroscopy (KBr pellet method) confirmed the presence ofcovalently bound fluorine (peaks in the 1220-12.50 cm⁻¹ region) in thesamples fluorinated, at temperatures of 250° C. and higher. No C—Fstretching frequency was seen for the sample fluorinated at 150° C. andits two-point resistance (5 mm apart) was ˜100 which therefore precludeslarge amounts of fluorine being covalently bound to the SWNT side wall.Product stoichiometries of the fluorination reactions are shown inTable 1. Discrepancies between the gravimetric and microprobe analysescan be attributed to product decomposition as described above,especially at the higher temperatures.

FIG. 1-A shows a TEM image of the purified, unreacted SWNT material.FIG. 1-B shows a TEM image of SWNT fluorinated at 325° C. As can be seenfrom the image, the tubes remain largely intact after treatment underthese conditions. FIG. 1-C is a TEM image of SWNT fluorinated at 500° C.Here it would appear that the tubes are essentially all destroyed.However, a fair number of nested tube-like graphic structuresreminiscent of multiwall carbon nanotubes (MWNT) seem to have beengenerated as a result of the high temperature reaction. These structuresare shown in FIG. 1-D.

The fluorination of MWNT has been reported previously (Hamwi, et al.,1997, Carbon, 35:723-728). This was done at two temperatures: 25° C. and500° C. The room temperature reaction was done with a F₂, HF and IF₅mixture and yielded an intercalated type compound. The reaction carriedout at 500° C. was done with F_(2,) and was determined to have destroyedthe tube structure to yield a graphite fluoride compound ofstoichiometry CF. In light of this, it is not too surprising thatdestruction of the SWNT was observed at 500° C., but somewhat surprisingthat MWNT-like structures are formed. The generation of these may be aconsequence of residual metal catalysts present in the sample.

TABLE 1 Reaction product stoichiometries determined by both gravimetricand electron microprobe analysis. Reaction temp.° C. 150 250 325 400 500600 gravimetric CF_(0.114) CF_(0.521) CF_(0.495) CF_(0.565) * microprobeCF_(0.097) CF_(0.458) CF_(0.554) CF_(0.647) CF_(0.815) CF_(0.99) *nodetermination at these temperatures.

1.2 Delfuorination of Single-Wall Carbon Nanotubes

Once fluorinated, SWNT were defluorinated with anhydrous hydrazine(Aldrich, 98%). To the pieces of “bucky paper”, fluorinated at 250° C.,325° C. and 400° C., was added 5 ml of hydrazine under an inertatmosphere at room temperature. The SWNT were allowed to sit in thehydrazine for one hour prior to filtering and washing with water.

As the Raman spectroscopy of SWNT has been well developed boththeoretically (Richter, et al., 1997, Phys, Rev. Lett., 79:2738-2741)and experimentally (Rao, et al., 1998, Science, 275:187-191), it wasused to examine the results of both the fluorination and subsequentdefluorination of the SWNT. FIG. 2 shows the Raman spectrum of the pure,unadulterated SWNT material. The smaller peak at 186 cm⁻¹ is due to acharacteristic breathing mode of the SWNT. Raman spectra of SWNTfluorinated for 5 hours at reaction temperatures of 250° C., 325° C. and400° C. are shown in FIG. 3. Trace A, corresponding to the reaction at250° C., shows only two broad peaks centered around 1340 cm⁻¹ and 1580cm⁻¹ and a broad band fluorescence. The Raman peaks correspond to sp³and sp² carbon stretching modes, respectively. At higher reaction temps,yielding high F to C ratios, these peaks disappear and the fluorescenceis attenuated. As C—F bonds are not very polarizable, it isunderstandable that they are not seen in the Raman spectra presentedhere.

Raman spectra of the defluorinated products of the SWNT originallyfluorinated at 250° C., 325° C. and 400° C. are shown in FIG. 4. TracesA, B and C correspond to the material originally fluorinated at 250° C.,325° C. and 400° C., respectively. As can be seen in traces A and B, thecharacteristic breathing mode at 186 cm⁻¹ returns upon defluorination.This is not true in trace C, indicating that the tubes are largelydestroyed at 400° C. Additionally, the peak at 1340 cm⁻¹ grows relativeto the characteristic SWNT peaks with increasing fluorinationtemperature. This can be attributed to one or both of the followingfactors: one, tubes are being “unzipped” much more readily at the highertemperatures and secondly, at higher reaction temperatures, a greateramount of decomposition of the type: CF₄, C₂F₄, C₂F₆, etc, is occurring.

SEM images and two-point resistivity measurements were obtained on asingle piece of “bucky paper” after each of the following stages:purification, fluorination at 325° C. and defluorination in hydrazine atroom temperature for one hour. FIG. 5-A shows the purified startingmaterial. FIG. 5-B shows the same piece after having been fluorinated at325° C. for 5 hours. The image shows excessive charging due to itsinsulating nature, but the “rope-like” structure of tubes is stillevident. Finally, FIG. 5-C shows the same piece of “bucky paper” afterhaving been defluorinated in hydrazine. The two-point resistance of thepurified starting material is 15-16 Ω measured 5 mm across the surfaceof the “bucky paper”. Identical measurements on the fluorinated anddefluorinated “bucky paper” yielded a resistance of >20 MΩ and 125-130 Ωrespectively. It is interesting to note that the defluorinated materialrecovers most, but not all of its original conductivity.

Example 2

2.1 Preparation of Fluorinated Single-Wall Carbon Nanotubes

SWNT were produced by the dual pulsed laser vaporization of Co/Ni dopedgraphite rods and purified as discussed previously (Rinzler, et al.,1998). The highly purified product consists of colloidally suspendedbundles or “ropes” of SWNT (Liu, et al., 1998). Filtering this over a0.2 micron PTFE filter membrane and rinsing with methanol yields a blackfilm that can be peeled off to give a freestanding “bucky paper.” Thispaper was then oven baked for several hours at 150° C. to remove anyresidual solvent. The baked “bucky paper” was then loaded into atemperature controlled monel flow reactor where it was purged at 250° C.under a stream of He for ˜1 hour. A 10% F₂ in He mixture was then passedover the sample after first being passed over NaF to remove any HFpresent. This yielded material with stoichiometries ranging from C₃F toC₂F (as determined by electron microprobe analysis) depending onreaction time (between 8 and 12 hours) and on the quantity beingfluorinated.

2.2 Methylated Single-Wall Carbon Nanotubes

Once fluorinated, the nanotubes were then placed in a reaction flaskunder a N₂ purge. Methyl lithium (1.4 M in diethyl ether, Aldrich) wasthen added in significant molar excess via syringe through a rubberseptum in the reaction flask. The reaction mixture was then refluxed forthree hours and after which, the methyl lithium was neutralized with awater/ether mixture. The resulting material was then filtered, washedwith 3M HCI (to remove LiF and LiOH) followed by methanol and then ovendried at 130° C. Electron microprobe analysis revealed the fluorinecontent of this material to be 3.7 atomic percent (down from around30%). SEM and TEM analysis confirmed that the rope and tube structuressurvived both the fluorination and methylation steps.

The Raman spectroscopy of SWNT is now well known (Rao, et al., 1998).Raman spectroscopy of the methylated nanotube product was obtained on aSpex Triplemate specrometer equipped with a CCD detector and using a514.5 nm Ar laser excitation source. The spectrum reveals thatsignificant alteration has taken place (FIG. 6). Pyrolysis of thismaterial in Ar at 700° C. regenerates the original SWNT as evidenced byits Raman spectrum. TGA of the pyrolysis process reveals a 25% mass lossupon heating to 700° C. EI mass spectroscopy of the pyrolysis productsreveals CH₃ groups to be the major species being evolved during thepyrolysis (FIG. 7) with the rest of the mass peaks being consistent withmethyl recombination pathways during pyrolysis.

The electrical properties of the SWNT change dramatically as they arefunctionalized. The untreated SWNT are essentially metallic and theirtwo point resistance (essentially a contact resistance, Bozhko, et al.,1998, Appl. Phys. A, 67:75-77) measured across 5 mm of the “bucky paper”surface is 10-15 Ω. When fluorinated, the tubes become insulating andthe two point resistance exceeds 20 M Ωm. After methylation the tubespossess a two point resistance of ˜20 kΩ. Pyrolysis of the methylatedproduct brings the resistance down to ˜100 Ω. Incomplete return of theelectrical conductivity upon pyrolysis may be due to an increasedcontact resistance that results from disorder induced into the ropelattice following the sequence of reaction steps.

The methylated SWNT could be suspended quite readily by sonication inchloroform. Dispersal of this suspension on a Si wafer followed by AFManalysis confirmed the nondestructive nature of the sonication process.Additionally, a large number of single tubes could be seen. This was nottrue of similarly exposed, untreated SWNT.

To get an infrared spectrum of the product, the dried methylatedmaterial was suspended in CDCl₃ and dispersed over KBr powder which wasthen dried and pressed into a pellet. By using deuterated chloroform weeliminated the possibility of seeing C—H stretching modes due to thepresence of residual solvent. IR analysis of the pellet revealed asignificant amount of C—H stretching in the ˜2950 cm⁻¹ region of thespectrum as shown in FIG. 8. Also present, however, is a significant C—Fstretching band indicating that not all of the fluorine had beendisplaced. This might be because the bulky methyl lithium cannotpenetrate the rope lattice to the extent that the fluorine could in theoriginal fluorination. Alternatively, the cage is likely to become lesselectronegative and, therefore, less susceptible to nucleophilic attackas successive fluorines are displaced (see Boltalina, et al., 1996, J.Chem. Soc., Perkin Trans., 2:2275-2278).

The methylated tubes were not suspendable in any of the nonpolarhydrocarbon solvents tried, although not all possibilities wereinvestigated. The fact that the suspendability of the methylated tubesin CHCl₃ is superior to that of the untreated tubes is interesting,however. Using a suitable solvent to suspend the methylated SWNT asindividual tubes capable of being manipulated individually, will havesignificant benefits. Alternatively, other nucleophiles, e.g. butyl, canbe substituted for the fluorine to render the SWNT more suspendable in asuitable solvent, which is equally significant.

In summary, SWNT were methylated by first fluorinating them and thenreacting the fluorinated product with methyl lithium. This methylationof fluorinated SWNT precursors proceeds through a novel nucleophilicsubstitution pathway that is capable of generating a wide range ofsubstituted SWNT products.

Example 3

3.1 Preparation of Highly Purified SWNTs

Single wall carbon nanotubes were produced by the dual pulsed laservaporization of Co/Ni doped graphite rods and purified by methodsdiscussed previously (Rinzler, et al., Appl. Phys.A, 1998, 67:9-37.).The SWNTs produced in this way are primarily (10,10) nanotubes. Thepurified product is a metastable colloidal suspension of SWNT “ropes”(bundles of tubes ranging from a few to 200 SWNTs, see Thess, et al.,Science 1996, 273, 483-487) in a 0.2% aqueous solution of Triton™ X-100surfactant. This was then filtered over a PTTE filter membrane(Sartorius, with 0.2 μm pore dimensions) and rinsed with methanol.Filtering this and rinsing with methanol leads to a final product whichis a freestanding “mat” or “bucky paper” of SWNTs that is approximately10 μm thick. Purity of the SWNTs was monitored via scanning electronmicroscopy (JEOL 6320F SEM). FIG. 9 shows a sample of typical purity.This product was then resuspended by sonication in dimethyl formamide(DMF; Fisher, HPLC grade). Such treatment is believed to “cut” the tubesat their defect sites and also seems to unravel the ropes somewhat,leading to bundles containing fewer SWNTs. This product was thenfiltered, rinsed and heated in an oven at 150° C. for 2 hours prior tofluorination. Sonication in DMF may result in smaller SWNT ropes andultimately lead to a more efficient fluorination.

3.2 Preparation of Fluorinated SWNTs

The purified nanotubes (5-10 mg in the form of bucky paper) were placedin a temperature controlled fluorination reactor constructed of Monel™and nickel. After sufficient purging in He (Trigas 99.995%) at 250° C.,fluorine (Air Products 98%, purified of HF by passing it over NaFpellets) was introduced. The fluorine flow was gradually increased to aflow rate of 2 sccm diluted in a He flow of 20 sccm. The fluorinationwas allowed to proceed for approximately 10 hours, at which point thereactor was brought to room temperature, and the fluorine flow wasgradually lowered. After the fluorine flow was completely halted, thereactor was purged at room temperature for approximately 30 minutesbefore removing the fluorinated product. The fluorinated SWNTs consistedof approximately 70 atomic percent carbon and 30 atomic percent fluorineas determined by electron microprobe analysis (EMPA, Cameca SX-50). Thisfluorinated product was well characterized with Raman, IR, SEM, TEM,resistance measurements and x-ray photoelectron spectroscopy (PhysicalElectronics PHI 5700 XPS using soft monochromatic A1 Kα (1486.7 eV)x-rays).

3.3 Solvation in Alcohols

Attempts to solubilize fluorotubes with the “like dissolves like”approach of sonicating and heating them in perfluorinated solvents metwith little success. Attempts were also made to solvate them in hydrogenbonding solvents. Recent studies on the hydrogen bonding capabilities ofalkyl fluorides suggest that the fluorine in such species are poorhydrogen bond acceptors (Dunitz, et al., R, Eur. J. Chem., 1997,3(1):89-98; Howard, et al., Tetrahedron, 1996, 52(38):12613-12622). TheF⁻ ion, however, is one of the best hydrogen bond acceptors available.The strength of the hydrogen bond formed between HF and F⁻ approximatesthat of a covalent bond (Harrell, et al., JA CS 1964, 86:4497). An XPSanalysis of our fluorinated SWNT product reveals an F is peak at abinding energy of 687 eV. Polytetrafluoroethylene has an F 1s bindingenergy of 691.5 eV. This suggests that the fluorine bonded to thefluorotubes is considerably more ionic than the fluorine present inalkyl fluorides (see Watanabe, et al., Graphite Fluorides, Elsevier:Amsterdam, 1988; p.246). Thus, the increased ionic nature of the C—Fbond in the fluorotubes may make the fluorine on it better hydrogen bondacceptors.

Sonication of the fluorinated SWNT material in alcohols was carried outby placing approximately 1 milligram of material into a vial containingapproximately 10 mL of alcohol solvent and sonicating for approximately10 minutes. Sonication was performed by partially immersing the cappedvial in a Cole-Parmer ultrasonic cleaner (containing water) operating at55 kHz. The solvated fluorotubes were then dispersed on a clean micasurface by means of a 3000 rpm rotary spinner (Headway Research, Inc.)and examined with atomic force microscopy (Digital Instruments MultimodeSPM). The solvated fluorotubes were also analyzed with a Shimadzu model1601PC UV-vis spectrometer using quartz cuvetts.

Fluorotubes were solvated by sonicating in alcohol solvents including:methanol, ethanol, 2,2,2-trifluoroethanol, 2-propanol, 2-butanol,n-pentanol, n-hexanol, cyclohexanol and n-heptanol. Sonicating thefluorotubes in alcohol solvents produced metastable solutions. Thesesolutions were stable for a couple of days to over one week, dependingon the concentration and solvent used. While typical sonication timeswere around 10 minutes, the heavier solvents (pentanol and up) requiredslightly longer sonication times m order to fully suspend the tubes. Ofthe solvents used, 2-propanol and 2-butanol seemed to solvate thefluorotubes the best with the solutions being stable for more than aweek. The solubility limit of the solvated “fluorotubes” in 2-propanolis at least 0.1 mg/mL. This solution was stable for slightly less than aweek with some particulate matter precipitating out after a few days.This suggests that pushing the solubility limit somewhat decreases thesolution's stability or that a super saturated solution can exist for ashorter period of time. All of the other solutions were stable for atleast a couple of days before the onset of precipitation. A likelyscenario for such solvation would be hydrogen bonding between thealcohol's hydroxyl hydrogen and the nanotubebound fluorine (scheme 1).No evidence of alkoxy substitution (or evolution of HF) was observed.

Efforts were also made to solvate the fluorotubes in other stronghydrogen bonding solvents like water, diethyl amine, acetic acid andchloroform. While water will not “wet” the fluorotube by itself, it willwith the addition of a small amount of acetone. Still, even longsonication times in this water/acetone mixture failed to solvate thefluorotubes. Likewise, neither diethylamine nor acetic acid wouldsolvate the fluorotubes. Chloroform solvated the tubes, but the solutionwas far less stable than those in alcohol solvents, with the fluorotubesfalling out of solution in less than an hour.

The solvated fluorotubes were filtered over a 0.2 micron PTFE filter.Once dry, the fluorotubes could be peeled off the paper to form afreestanding film. This film was then examined by Raman spectroscopy(Jobin Yvon-Spex model HR 460 monochrometer coupled with an ISA SpectrumONE series CCD detector and using 514.5 nm excitation from a Liconix Arlaser) and by EMPA to determine whether or not any reaction had takenplace on the basis of the composition of the product. Fluorotubes fromall of the solutions (except those in cyclohexanol, n-hexanol andn-heptanol) were examined with atomic force microscopy. FIG. 10 shows anAFM scan of fluorotubes that had been dissolved in 2-butanol and thendipersed on a clean mica surface. This result is fairly typical of allthe fluorotube/alcohol solutions that were examined with AFM. Almost allthe tubes are believed to be solvated, as few “ropes” (bundles of tubes)are present.

Some of these solutions were examined with ¹⁹F-NMR, but this proved tobe rather uninformative. It yielded a broad peak centered at around −175ppm. While this is indicative of fluorine being present, the broadeningis due to either a wide variety of F environments (as seen in theinhomogeneous fluorination of C₆₀, Kniaz, et al., J. Am. Chem. Soc.,1993, 115:6060-6064) or of insufficient “tumbling” while in solution. Noinformation regarding the possible hydrogen bonding environments couldbe obtained with this method.

Filtering a solution of fluorotubes in isopropyl alcohol over a PTFEfilter and examining the tubes with EMPA revealed no presence of oxygenand only slightly lower fluorine levels (C/F atomic percent ratio=72/28compared with 70/30 for the starting material). This would suggest thatthe solvation process is not the result of a chemical reaction, but isinstead the result of hydrogen bonding between the alcohol and thefluorines on the nanotube surface. Analysis of fluorotubes sonicated formuch longer times (2 hours) showed reduced levels of fluorine (C/Fatomic percent ratio=76/24), yet they remained solvated. Apparently,ultrasonication can lead to removal of some of the fluorine if allowedto progress long enough. The fluorotubes were sonicated continuously inisopropanol and monitored with UV-vis absorption spectroscopy forsonication time t=10 minutes and every 30 minutes after that. Aftersonication for 40 minutes the solution exhibited an absorption band at204 nm. This band continued to grow and to red shift to lower energy asthe sonication proceeded and fluorine was presumably being eliminated.After sonicating for 130 minutes the peak had increased in intensity andshifted to 237 nm (FIG. 11).

3.4 Reactions in Solution

The present inventors shown that hydrazine acts as a effectivedefluorinating agent. Anhydrous hydrazine (Aldrich, 98%) was added tothe solvated fluorotubes. The reaction mixture was continually stirredwith a glass stir bar for a period of about an hour. The reactionmixture was filtered, rinsed with methanol and allowed to dry. Thisproduct was then examined with EMPA and Raman spectroscopy. It was alsosuspended in dimethyl formamide, dispersed on a mica surface andexamined with AFM. The instruments and procedures were as above.

Adding anhydrous hydrazine to a solution of fluorotubes in isopropanolcaused them to immediately precipitate out of solution. Filtering thesolution after letting it sit for an hour yielded a product of very lowfluorine content, as determined by EMPA (C/F atomic percent ratio=93/7).Unreacted SWNTs are known to suspend fairly well in DMF. Suspending thisproduct in DMF and dispersing it on a mica surface followed by AFManalysis yielded tubes very reminiscent of the starting material (FIGS.12, a & b).

Raman spectroscopy of SWNTs has been well established (Richter, E., etal., Phys. Rev. Lett., 1997, 79(14):2738-2741; Rao, et al., Science,1997, 275:187-191; Fang, et al., J. Mat. Res., 1998, 13:2405-2411), andit was used as a probe to follow the starting material through thefluorination, sonication and defluorination. Raman spectroscopy on thehydrazine-defluorinated product yields a spectrum similar to thestarting material and very different from the fluorinated SWNTs (FIGS.13; ab & c).

Fluorotubes were also sonicated in a 0.5 M sodium methoxide in methanolsolution (Aldrich, A.C.S. reagent) for approximately 10 minutes. Thetubes broke up and appeared to be suspended but quickly fell out ofsolution upon standing. This too was filtered, rinsed and examined withEMPA and El mass spectroscopy (Finnigan MAT 95).

Sonication of the fluorotubes in a sodium methoxide in methanol solutionfor two hours resulted in the tubes precipitating out of solution. Afterthe filtered product was rinsed with water (to remove NaF) and methanol,then dried in an oven at 140° C. for half an hour, it was analyzed withEMPA which revealed the C/F/O relative atomic percents to be 79/17/4.This varies considerably from the starting material which had C/F/Orelative atomic percents of 66/33.7/0.3 and suggests a productsoichiometry of C_(4.4)F(OCH₃)_(0.25). Pyrolysis of this product with ahigh temperature probe inside a mass spectrometer, followed by electronionization, yielded significant quantities of methoxy ions (m/z=31)coming off primarily at 650-700° C. as determined by the residual ioncurrent trace. The high temperature for evolution indicates that themethoxy groups seen were originally strongly bonded to the nanotube. Ifthe oxygen ratios seen by EMPA are reflective of the number of methoxygroups present on the nanotabe, it may be concluded that the majority ofthese would have to be bonded to the nanotube side wall, based on thefact that the number of nanotube end carbons is extremely small relativeto the number of side wall carbons.

Nucleophilic attack on the fluorinated nanotube by a methoxy anion is aplausible scenario as nucleophilic attack of this type has been welldocumented in the case of fluorinated fullerenes (Mickelson, et al., JFluorine Chem 1998, 92(1):59-62; Taylor, et al., J. Chem. Soc., Chem.Commun. 1992,665-667). The C—F bonds on fluorinated fullerenes (andcarbon nanotubes) are weakened relative to the C—F bonds in alkylfluorides due to an “eclipsing strain effect” (Taylor, R,. RussianChemical Bulletin, Engl. Ed. 1998, 47(5):823-832). A nucleophilic attackof this type is likely to occur via attack on an electropositive carbonbeta to a carbon with fluorine attached to it as shown in scheme 2. Thisis rationalized by the fact that an S_(N)1 type substitution isenergetically unfavorable and backside attack, as in an S_(N)2 typemechanism, is impossible (Taylor, R The Chemistry of the Fullerenes(Edited by R. Taylor), World Scientific Publishing, London, 1995;pp.208-209).

An application of particular interest for a homogeneous population ofSWNT molecules is production of a substantially two-dimensional arraymade up of single-walled nanotubes aggregating (e.g., by van der Waalsforces) in substantially parallel orientation to form a monolayerextending in directions substantially perpendicular to the orientationof the individual nanotubes. Formation of such arrays is substantiallyenabled by derivatization of both the ends and side walls of nanotubesas is indicated below. Such monolayer arrays can be formed byconventional techniques employing “self-assembled monolayers” (SAM) orLangmiur-Blodgett films, see Hirch, pp. 75-76. Such a molecular array isillustrated schematically in FIG. 14. In this figure, derivatizednanotubes 1 are bound via interaction of the linking or complexingmoiety attached to the nanotube to a substrate 2 having a reactivecoating 3 (e.g., gold). Sidewall derivatization in this application canfacilitate assembly of the array by enabling the tubes to moveeffectively together as the array assembles.

Typically, SAMs are created on a substrate which can be a metal (such asgold, mercury or ITO (indium-tin-oxide)). The molecules of interest,here the SWNT molecules, are linked (usually covalently) to thesubstrate through a linker moiety such as —S—, —S—(CH₂)_(n)—NH—,—SiO₃(CH₂)₃NH— or the like. The linker moiety may be bound first to thesubstrate layer or first to the SWNT molecule (at an open or closed end)to provide for reactive self-assembly. Langmiur-Blodgett films areformed at the interface between two phases, e.g., a hydrocarbon (e.g.,benzene or toluene) and water. Orientation in the film is achieved byemploying molecules or linkers that have hydrophilic and lipophilicmoieties at opposite ends. The configuration of the SWNT molecular arraymay be homogenous or heterogeneous depending on the use to which it willbe put. Using SWNT molecules of the same type and structure provides ahomogeneous array of the type shown in FIG. 14. By using different SWNTmolecules, either a random or ordered heterogeneous structure can beproduced. An example of an ordered heterogeneous array is shown in FIG.15 where tubes 4 are (n,n), i.e., metallic in structure and tubes 5 are(m,n), i.e., insulating. This configuration can be achieved by employingsuccessive reactions after removal of previously masked areas of thereactive substrate.

Arrays containing from 10³ up to 10¹⁰ and more SWNT molecules insubstantially parallel relationships can be used per se as a nanoporousconductive molecular membrane, e.g., for use in fuel cells and inbatteries such as the lithium ion battery. This membrane can also beused (with or without attachment of a photoactive molecule such ascis-(bisthiacyanato bis (4,4′-dicarboxy-2-2′-bipyridine Ru (II)) toproduce a highly efficient photo cell of the type shown in U.S. Pat. No.5,084,365.

One preferred use of the SWNT molecular arrays of the present inventionis to provide a “seed” or template for growth of macroscopic carbonfiber of single-wall carbon nanotubes as described below. The use of amacroscopic cross section in this template is particularly useful forkeeping the live (open) end of the nanotubes exposed to feedstock duringgrowth of the fiber. The template array of this invention can be used asformed on the original substrate, cleaved from its original substrateand used with no substrate (the van der Waals forces will hold ittogether) or transferred to a second substrate more suitable for theconditions of fiber growth.

Where the SWNT molecular array is to be used as a seed or template forgrowing macroscopic carbon fiber as described below, the array need notbe formed as a substantially two-dimensional array. The “seed” arraycan, for instance, be the end of a fiber of parallel nanotubes in vander Walls contact that has been cut, or a short segment of such a fiberthat has been cut from the fiber. For such substrates the surfacecomprising the ends of must be prepared to be clean and flat bypolishing and or electrochemical etching to achieve a clean, highlyplanar surface of exposed nanotube ends. Any form of array that presentsat its upper surface a two-dimensional array can be employed. In thepreferred embodiment, the template molecular array is a manipulatablelength of macroscopic carbon fiber as produced below.

Large arrays (i.e., >10⁶ tubes) also can be assembled using nanoprobesby combining smaller arrays or by folding linear collections of tubesand/or ropes over (i.e., one folding of a collection of n tubes resultsin a bundle with 2n tubes).

Growth of Nanotubes from “Seeds”

The present invention provides methods for growing continuous carbonfiber from SWNT molecular arrays to any desired length. The carbon fiberwhich comprises an aggregation of substantially parallel carbonnanotubes may be produced according to this invention by growth(elongation) of a suitable seed molecular array. As used herein, theterm “macroscopic carbon fiber” refers to fibers having a diameter largeenough to be physically manipulated, typically greater than about 1micron and preferably greater than about 10 microns.

It is well known that SWNT formation occurs at temperatures between 500and 2000° C. in which a catalytic particle comprising group VI B or VIIIB Btransition metals (individually or as a mixture) resides at the endof a “growing” SWNT. The catalytic particle interacts with acarbon-bearing feedstock to promote chemical processes by which carbonin the feedstock is converted into carbon organized in the structureknown as a SWNT. Once a SWNT of a specific geometry (chirality anddiameter) begins to grow, the tube geometry remains fixed. The catalytictube-growth process is most effectively promoted by catalyst particlesof an appropriate size range and chemical composition. Examples in theart indicate that the most effective catalyst particles have diametersapproximately equal to those of the growing nanotubes, and that theycomprise a single metal or a mixture of metals. An objective of thisinvention is to provide processes by which a suitable catalyst particlemay be formed at the end of an existing SWNT, enabling growth of thattube to be initiated upon introduction of the tube/catalyst-particleassembly to an appropriate environment.

To achieve the objective, the invention provides methods for assemblingcatalyst particles on the ends of individual fullerene single-wallnanotubes (SWNT) in a way that supports further growth of the SWNT.Deliberate initiation of SWNT growth from such “seed” tubes is useful inthat:

1) it can act to produce nanotubes that have the same geometry as the“seed” tubes. [It is well known that fullerene single wall nanotubes(SWNT) may be formed with different geometries (different diameters andarrangements of carbon atoms with respect to the tube axis), and thatthe physical properties (e.g., electrical conductivity) of these tubesgenerally depend on these geometries]. Control of the tube geometrypermits growth of SWNT for applications that require specific materialproperties.

2). It can serve as an enabling process in bulk production of nanotubes;

3) It can enable growth of ordered structures of SWNT that have beenassembled by other means (e.g., suitable arrays can be formed byconventional techniques employing “self-assembled monolayers” (SAM) orLangmiur-Blodgett films, see Hirch, pp. 75-76.

4) It can be used to grow structural shapes of SWNT material comprisingparallel nanotubes all in van der Waals contact. These materials canhave the forms of sheets, I-beams, channels, etc. by appropriatelyconfiguring the seed in the shape of the cross section of the desiredstructural object.

To achieve the objectives and provide the benefits of growth from“seeds,” the present invention provides:

1) A measured amount of a transition-metal-containing species ischemically attached (by covalent bonding, chemisorption, physisorptionor combination thereof) to the sidewall of an individual SWNT segment orto the sidewalls of a group of SWNT segments. A preferred embodiment isone in which the metal is contained as a compound that is stable toexposure to moisture and air. The amount of metal attached to the SWNTsegment is determined by the degree of derivatization, which is definedherein as the number of derivative sites per nanometer of tube length.In this invention, the preferred degree of derivatization isapproximately 1 per nanometer, and the preferred method ofderivatization is covalent bonding of a species that contains a metalatom. Alternatively, the transition metal may be deposited directly onthe surface from metal vapor introduced onto the open tube ends of the“seed”.

2) Chemical or physical processing of the metal or metal-containingspecies in a way that allows metal atoms to aggregate at or near the endof the tube segment so that the aggregate is a suitable catalyst forenabling growth of the tube when the tube/catalyst assembly isintroduced to an appropriate environment.

3) Growth of nanotubes of specific geometries (chirality and diameter)by choosing the diameter and chirality of the “seed” tube.

4) Growth of organized structures of SWNT (e.g., arrays of tubes withspecific relative spacing and orientation of individual tubes, membranesof tubes comprising many parallel tubes closely packed together, androds or fibers of tubes with parallel axes) in which an initialstructure has been assembled by other means, which include the operationof molecule agencies attached to the sidewalls of the SWNTs forming thestructure, and the novel compositions of matter so produced.

5) Growth of organized structures of SWNT (as 4 above) in which the SWNTall have the same geometry (chirality and diameter) and the compositionof matter so produced.

6) Growth of organized structures of SWNT (as 4 above) in which the SWNTall have a range of geometries chosen to perform a specific function(e.g., a core of tubes of conducting geometry surrounded by tubes oflarge-gap semiconducting geometry to effect a small “insulated wire”)and the structures so produced.

7) Production of “monoclonal” batches of tubes that all have preciselythe same geometry because they all are grown from segments of a singletube which has been cut by known techniques and the compositions ofmatter so produced.

The present invention is further exemplified by the following:

a) A process in which one cuts segments of SWNT of 0.1 to 1 micronlength by, for instance, sonicating the SWNT material indimethylformamide, selects tube segments of a specific range of lengthand covalently bonds a chelating agent such as ethylene to the tubewall. These binding sites are sufficiently spaced from one another thatthe number of chelating agent molecules is roughly equivalent to thenumber of metal atoms needed to form an active catalyst cluster at theend of the tube segment. Covalent bonding of various species isdescribed herein, via replacement reactions upon a small fraction of thederivatized sites on fluorinated tubes. A chelating agent is reactedwith a fluorinated SWNT so that the chelating agent replaces fluorine onthe nanotube, followed by washing the derivatized nanotube with a weaksolution of metal ions in water (e.g., Fe³⁺). The interaction of the Feand water with the chelating agent will form a complex on the tubesurface that is stable under exposure to air and water. The tubematerial can be heated in a reducing atmosphere (such as H₂). Thisheating will cause the chelating agent to react by converting to gaseousproducts, leaving Fe adsorbed on the tube wall, and at appropriatetemperatures the Fe will migrate along the tube walls. The tube endpresents an irregularity of the surface upon which the Fe is migrating,and the Fe will preferentially collect there as an aggregate suitablefor functioning as a catalyst particle for tube growth.

b) Approaches similar to a) above, but including more complex,multidentate ligands such as ethydiamine tetra-acetic acid (EDTA) orbipyridine tethered to the side of the SWNT by a covalent linkage orsimpler species such as a carboxylate or OH group.

c) Another means for assembly of a catalytic particle at the end of anSWNT segment involves reaction processes in which chelating agents,other ligands, or metal containing species themselves, are chemicallyattached to the tube ends (both open and closed). As described above,the tube ends are more active sites and support a broader range ofchemical processes than the tube sidewalls. Both ion-exchange andcovalent attachment of metal-bearing proteins (e.g. metallothionein) ormetal-bearing complexes are possible examples. One can, for example,exchange the metal atoms for the carboxylic acid groups known to existat the ends of tubes, directly attached metal bearing proteins or othermetal-containing species with the tube ends. If necessary furtherprocesses can enable deposition of additional metal at the ends of thetube segments. The amount of metal is simply determined by the usualmethods of control of the reagent concentrations, temperatures, andreaction times. Here, again, aggregates of metal atoms of theappropriate size are formed at the end of selected SWNT segments, andcan serve as catalysts for tube growth under the appropriate conditions.

d) Formation of arrays of SWNT wherein the array formation is enabledand controlled by species attached to the tube sidewalls. This speciesthat enables array formation may be attached to the tube by covalentbonding, chemisorption, adsorption, or a combination thereof. Thisaspect of this invention:

i) enables and controls organization of SWNT segments into organizedstructures and

ii) admits metal-containing species or metal atoms or ions to the tubesidewalls in a way that under appropriate chemical processing the metalparticles may migrate to the tube ends and form catalysts for furtherSWNT growth.

The first step in the growth process is to open the growth end of theSWNTs in the molecular array. This can be accomplished as describedabove with an oxidative and/or electrochemical treatment. Next, atransition metal catalyst is added to the open-ended seed array. Thetransition metal catalyst can be any transition metal that will causeconversion of the carbon-containing feedstock described below intohighly mobile carbon radicals that can rearrange at the growing edge tothe favored hexagon structure. Suitable materials include transitionmetals, and particularly the Group VI B or VIII B transition metals,i.e., chromium (Cr), molybdenum (Mo), tungsten (W), iron (Fe), cobalt(Co), nickel (Nl), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium(Os), iridium (Ir) and platinum (Pt). Metals from the lanthanide andactinide series may also be used. Preferred are Fe, Ni, Co and mixturesthereof. Most preferred is a 50/50 mixture (by weight) of Ni and Co.

The catalyst should be present on the open SWNT ends as a metal clustercontaining from about 10 metal atoms up to about 200 metal atoms(depending on the SWNT molecule diameter). Typically, the reactionproceeds most efficiently if the catalyst metal cluster sits on top ofthe open tube and does not bridge over adjacent tubes. Preferred aremetal clusters having a cross-section equal to from about 0.5 to about1.0 times the tube diameter (e.g., about 0.7 to 1.5 nm).

In the preferred process, the catalyst is formed, in situ, on the opentube ends of the molecular array by a vacuum deposition process. Anysuitable equipment, such as that used in Molecular Beam Epitaxy (MBE)deposition, can be employed. One such device is a Küdsen Effusion SourceEvaporator. It is also possible to effect sufficient deposition of metalby simply heating a wire in the vicinity of the tube ends (e.g., a Ni/COwire or separate Ni and CO wires) to a temperature below the meltingpoint at which enough atoms evaporate from one wire surface (e.g., fromabout 900 to about 1300° C.). The deposition is preferably carried outin a vacuum with prior outgassing. Vacuums of about 10⁻⁶ to 10⁻⁸ Torrare suitable. The evaporation temperature should be high enough toevaporate the metal catalyst. Typically, temperatures in the range of1500 to 2000° C. are suitable for the Ni/Co catalyst of the preferredembodiment. In the evaporation process, the metal is typically depositedas monolayers of metal atoms. From about 1-10 monolayers will generallygive the required amount of catalyst. The deposition of transition metalclusters on the open tube tops can also be accomplished by laservaporization of metal targets in a catalyst deposition zone.

The actual catalyst metal cluster formation at the open tube ends iscarried out by heating the tube ends to a temperature high enough toprovide sufficient species mobility to permit the metal atoms to findthe open ends and assemble into clusters, but not so high as to effectclosure of the tube ends. Typically, temperatures of up to about 500° C.are suitable. Temperatures in the range of about 400-500° C. arepreferred for the Ni/Co catalysts system of one preferred embodiment.

In a preferred embodiment, the catalyst metal cluster is deposited onthe open nanotube end by a docking process that insures optimum locationfor the subsequent growth reaction. In this process, the metal atoms aresupplied as described above, but the conditions are modified to providereductive conditions, e.g., at 800° C., 10 millitorr of H₂ for 1 to 10minutes. There conditions cause the metal atom clusters to migratethrough the system in search of a reactive site. During the reductiveheating the catalyst material will ultimately find and settle on theopen tube ends and begin to etch back the tube. The reduction periodshould be long enough for the catalyst particles to find and begin toetch back the nanotubes, but not so long as to substantially etch awaythe tubes. By changing to the above-described growth conditions, theetch-back process is reversed. At this point, the catalyst particles areoptimally located with respect to the tube ends since they already werecatalytically active at those sites (albeit in the reverse process).

The catalyst can also be supplied in the form of catalyst precursorswhich convert to active form under growth conditions such as oxides,other salts or ligand stabilized metal complexes. As an example,transition metal complexes with alkylamines (primary, secondary ortertiary) can be employed. Similar alkylamine complexes of transitionmetal oxides also can be employed. The catalyst can also be added to thefree ends by causing migration of metal atoms derived from side wallpendant groups added as described above.

In the next step of the process of the present invention, the SWNTmolecular array with catalyst deposited on the open tube ends issubjected to tube growth (extension) conditions. This may be in the sameapparatus in which the catalyst is deposited or a different apparatus.The apparatus for carrying out this process will require, at a minimum,a source of carbon-containing feedstock and a means for maintaining thegrowing end of the continuous fiber at a growth and annealingtemperature where carbon from the vapor can be added to the growing endsof the individual nanotubes under the direction of the transition metalcatalyst. Typically, the apparatus will also have means for continuouslycollecting the carbon fiber. The process will be described forillustration purposes with reference to the apparatus shown in FIGS. 16and 17.

The carbon supply necessary to grow the SWNT molecular array into acontinuous fiber is supplied to the reactor 10, in gaseous form throughinlet 11. The gas stream should be directed towards the front surface ofthe growing array 12. The gaseous carbon-containing feedstock can be anyhydrocarbon or mixture of hydrocarbons including alkyls, acyls, aryls,aralkyls and the like, as defined above. Preferred are hydrocarbonshaving from about 1 to 7 carbon atoms. Particularly preferred aremethane, ethane, ethylene, actylene, acetone, propane, propylene and thelike. Most preferred is ethylene. Carbon monoxide may also be used andin some reactions is preferred. Use of CO feedstock with transitionmetal catalysts is believed to follow a different reaction mechanismthan that proposed for most other feedstock gasses. See Dai, et al.,1996.

The feedstock concentration is preferably as chosen to maximize the rateof reaction, with higher concentrations of hydrocarbon giving fastergrowth rates. In general, the partial pressure of the feedstock material(e.g., ethylene) can be in the 0.001 to 1000.0 Torr range, with valuesin the range of about 1.0 to 10 Torr being preferred. The growth rate isalso a function of the temperature of the growing array tip as describedbelow, and as a result growth temperatures and feed stock concentrationcan be balanced to provide the desired growth rates. A preferredfeedstock in many instances is CO, in which case the optimal pressuresare in the range of 10 to 100 atmospheres.

It is not necessary or preferred to preheat the carbon feedstock gas,since unwanted pyrolysis at the reactor walls can be minimized thereby.The only heat supplied for the growth reaction should be focused at thegrowing tip of the fiber 12. The rest of the fiber and the reactionapparatus can be kept at room temperature. Heat can be supplied in alocalized fashion by any suitable means. For small fibers (<1 mm indiameter), a laser 13 focused at the growing end is preferred (e.g., aC—W laser such as an argon ion laser beam at 514 nm). For larger fibers,heat can be supplied by microwave energy or R—F energy, again localizedat the growing fiber tip. Any other form of concentrated electromagneticenergy that can be focused on the growing tip can be employed (e.g.,solar energy). Care should be taken, however, to avoid electromagneticradiation that will be absorbed to any appreciable extent by thefeedstock gas.

The SWNT molecular array tip should be heated to a temperaturesufficient to cause growth and efficient annealing of defects in thegrowing fiber, thus forming a growth and annealing zone at the tip. Ingeneral, the upper limit of this temperature is governed by the need toavoid pyrolysis of the feedstock and fouling of the reactor orevaporation of the deposited metal catalyst. For most feedstocks andcatalysts, this is below about 1300° C. The lower end of the acceptabletemperature range is typically about 500° C., depending on the feedstockand catalyst efficiency. Preferred are temperatures in the range ofabout 500° C. to about 120⁰° C. More preferred are temperatures in therange of from about 700° C. to about 1200° C. Temperatures in the rangeof about 900° C. to about 1100° C. are the most preferred, since atthese temperatures the best annealing of defects occurs. The temperatureat the growing end of the cable is preferably monitored by, andcontrolled in response to, an optical pyrometer 14, which measures theincandescence produced. While not preferred due to potential foulingproblems, it is possible under some circumstances to employ an inertsweep gas such as argon or helium.

In general, pressure in the growth chamber can be in the range of 1millitorr to about 1 atmosphere. The total pressure should be kept at 1to 2 times the partial pressure of the carbon feedstock. A vacuum pump15 may be provided as shown. It may be desirable to recycle thefeedstock mixture to the growth chamber. As the fiber grows it can bewithdrawn from the growth chamber 16 by a suitable transport mechanismsuch as drive roll 17 and idler roll 18. The growth chamber 16 is indirect communication with a vacuum feed lock zone 19.

The pressure in the growth chamber can be brought to atmospheric, ifnecessary, in the vacuum feed lock by using a series of chambers 20.Each of these chambers is separated by a loose TEFLON O-ring seal 21surrounding the moving fiber. Pumps 22 effect the differential pressureequalization. A take-up roll 23 continuously collects the roomtemperature carbon fiber cable. Product output of this process can be inthe range of 10⁻³ to 10¹ feet per minute or more. By this process, it ispossible to produce tons per day of continuous carbon fiber made up ofSWNT molecules.

Growth of the fiber can be terminated at any stage (either to facilitatemanufacture of a fiber of a particular length or when too many defectsoccur). To restart growth, the end may be cleaned (i.e., reopened) byoxidative etching (chemically or electrochemically). The catalystparticles can then be reformed on the open tube ends, and growthcontinued.

The molecular array (template) may be removed from the fiber before orafter growth by macroscopic physical separation means, for example bycutting the fiber with scissors to the desired length. Any section fromthe fiber may be used as the template to initiate production of similarfibers.

The continuous carbon fiber of the present invention can also be grownfrom more than one separately prepared molecular array or template. Themultiple arrays can be the same or different with respect to the SWNTtype or geometric arrangement in the array. Large cable-like structureswith enhanced tensile properties can be grown from a number of smallerseparate arrays as shown in FIG. 18. In addition to the masking andcoating techniques described above, it is possible to prepare acomposite structure, for example, by surrounding a central core array ofmetallic SWNTs with a series of smaller circular non-metallic SWNTarrays arranged in a ring around the core array as shown in FIG. 19.

Not all the structures contemplated by this invention need be round oreven symmetrical in two-dimensional cross section. It is even possibleto align multiple molecular array seed templates in a manner as toinduce nonparallel growth of SWNTs in some portions of the compositefiber, thus producing a twisted, helical rope, for example. It is alsopossible to catalytically grow macroscopic carbon fiber in the presenceof an electric field to aid in alignment of the SWNTs in the fibers, asdescribed above in connection with the formation of template arrays.

Random Growth of Carbon Fibers From SWNTs

While the continuous growth of ordered bundles of SWNTs described aboveis desirable for many applications, it is also possible to produceuseful compositions comprising a randomly oriented mass of SWNTs, whichcan include individual tubes, ropes and/or cables. The random growthprocess has the ability to produce large quantities, i.e., tons per day,of SWNT material.

In general the random growth method comprises providing a plurality ofSWNT seed molecules that are supplied with a suitable transition metalcatalyst as described above, including the use of side wallderivatization to supply the catalyst moiety and subjecting the seedmolecules to SWNT growth conditions that result in elongation of theseed molecule by several orders of magnitude, e.g., 10² to 10¹⁰ or moretimes its original length.

The seed SWNT molecules can be produced as described above, preferablyin relatively short lengths, e.g., by cutting a continuous fiber orpurified bucky paper. In a preferred embodiment, the seed molecules canbe obtained after one initial run from the SWNT felt produced by thisrandom growth process (e.g., by cutting). The lengths do not need to beuniform and generally can range from about 5 nm to 10 μm in length.

These SWNT seed molecules may be formed on macroscale or nanoscalesupports that do not participate in the growth reaction. In anotherembodiment, SWNTs or SWNT structures can be employed as the supportmaterial/seed. For example, the self assembling techniques describedbelow can be used to form a three-dimensional SWNT nanostructure.Nanoscale powders produced by these techniques have the advantage thatthe support material can participate in the random growth process.

The supported or unsupported SWNT seed materials can be combined with asuitable growth catalyst as described above, by opening SWNT moleculeends and depositing a metal atom cluster. Alternatively, the growthcatalyst can be provided to the open end or ends of the seed moleculesby evaporating a suspension of the seeds in a suitable liquid containinga soluble or suspended catalyst precursor. For example, when the liquidis water, soluble metal salts such as Fe (NO₃)₃, Ni (NO₃)₂ or CO (NO₃)₂and the like may be employed as catalyst precursors. In order to insurethat the catalyst material is properly positioned on the open end(s) ofthe SWNT seed molecules, it may be necessary in some circumstances toderivatize the SWNT ends with a moiety that binds the catalystnanoparticle or more preferably a ligand-stabilized catalystnanoparticle.

In the first step of the random growth process the suspension of seedparticles containing attached catalysts or associated with dissolvedcatalyst precursors is injected into an evaporation zone where themixture contacts a sweep gas flow and is heated to a temperature in therange of 250-500° C. to flash evaporate the liquid and provide anentrained reactive nanoparticle (i.e., seed/catalyst). Optionally thisentrained particle stream is subjected to a reduction step to furtheractivate the catalyst (e.g., heating from 300-500° C. in H₂). Acarbonaceous feedstock gas, of the type employed in the continuousgrowth method described above, is then introduced into the sweepgas/active nanoparticle stream and the mixture is carried by the sweepgas into and through a growth zone.

The reaction conditions for the growth zone are as described above,i.e., 500-1000° C. and a total pressure of about one atmosphere. Thepartial pressure of the feedstock gas (e.g., ethylene, CO) can be in therange of about 1 to 100 Torr for ethylene or 1 to 100 atmospheres forCO. The reaction with pure carbon or hydrocarbon feedstocks ispreferably carried out in a tubular reactor through which a sweep gas(e.g., argon) flows.

The growth zone may be maintained at the appropriate growth temperatureby 1) preheating the feedstock gas, 2) preheating the sweep gas, 3)externally heating the growth zone, 4) applying localized heating in thegrowth zone, e.g., by laser or induction coil, or any combination of theforegoing.

Downstream recovery of the product produced by this process can beeffected by known means such as filtration, centrifugation and the like.Purification may be accomplished as described above. Felts made by thisrandom growth process can be used to make composites, e.g., withpolymers, epoxies, metals, carbon (i.e., carbon/carbon materials) andhigh −T_(c) superconductors for flux pinning.

What is claimed is:
 1. A method comprising: (i) derivatizing a sidewallof single wall carbon nanotubes with substituents; and (ii) assemblingan array of the single wall carbon nanotubes.
 2. The method of claim 1,removing at least some of the substituents that were derivatized to thesidewall of the single wall carbon nanotubes.
 3. The method of claim 1,further comprising utilizing the array of single-wall carbon nanotubesfor catalytic production of assemblies of single wall carbon nanotubes.4. The method of claim 1, further comprising reacting the single wallcarbon nanotubes with a fluorinating agent prior to derivatization. 5.The method of claim 1, wherein the single wall carbon nanotubes areassembled in a generally parallel configuration.
 6. The method of claim1, wherein the single wall carbon nanotubes are approximately of equallength and wherein each of the single wall carbon nanotubes has at leastone free end.
 7. The method of claim 5, wherein the single wall carbonnanotubes are approximately of equal length and wherein each of thesingle wall carbon nanotubes has at least one free end.
 8. The method ofclaim 1, further comprising exposing the single wall carbon nanotubes toa feedstock to grow the single wall carbon nanotubes.
 9. The method ofclaim 5, further comprising: (i) exposing the single wall carbonnanotubes to feedstock; and (ii) growing the single wall carbonnanotubes.
 10. The method of claim 7, further comprising: (i) exposingthe free ends of the single wall carbon nanotubes to feedstock; and (ii)growing the single wall carbon nanotubes.
 11. The method of claim 1,wherein on the sidewall of each of the single wall carbon nanotubes isdisposed a quantity of bonded transition metal catalyst precursormoieties sufficient to provide active catalyst metal atom clusters togrow single wall carbon nanotubes under conditions that promote thegeneration of metal atoms and the migration of said metal atoms to thefree ends of said single wall carbon nanotubes.
 12. The method of claim11, wherein at least some of the transition metal catalyst precursormoeities are physisorbed bonded to the single wall carbon nanotubes. 13.The method of claim 11, wherein at least some of the transition metalcatalyst precursor moeities are covalently bonded to the single wallcarbon nanotubes.
 14. The method of claim 5, wherein on the sidewall ofeach of the single wall carbon nanotubes is disposed a quantity ofbonded transition metal catalyst precursor moieties sufficient toprovide active catalyst metal atom clusters to grow single wall carbonnanotubes under conditions that promote the generation of metal atomsand the migration of said metal atoms to the free ends of said singlewall carbon nanotubes.
 15. The method of claim 9, wherein on thesidewall of each of the single wall carbon nanotubes is disposed aquantity of bonded transition metal catalyst precursor moietiessufficient to provide active catalyst metal atom clusters to grow singlewall carbon nanotubes under conditions that promote the generation ofmetal atoms and the migration of said metal atoms to the free ends ofsaid single wall carbon nanotubes.
 16. The method of claim 10, whereinon the sidewall of each of the single wall carbon nanotubes is disposeda quantity of bonded transition metal catalyst precursor moietiessufficient to provide active catalyst metal atom clusters to grow singlewall carbon nanotubes under conditions that promote the generation ofmetal atoms and the migration of said metal atoms to the free ends ofsaid single wall carbon nanotubes.
 17. An array comprising: (i) singlewall carbon nanotubes; (ii) fluorine, wherein the fluorine is covalentlybonded to the sidewall of the single wall carbon nanotubes.
 18. Thearray of claim 17, wherein the array is a membrane.
 19. The array ofclaim 17, wherein the amount of fluorine bonded to carbon atoms of thesingle wall carbon nanotubes is at a fluorine to carbon ratio of from(a) one fluorine atom to about 26 carbon atoms to (b) one fluorine atomto about two carbon atoms.
 20. The array of claim 19, wherein the amountof fluorine bonded to the carbon atoms of the single wall carbonnanotubes is at the fluorine to carbon ratio of from (a) one fluorineatom to about ten carbon atoms to (b) one fluorine atom to about twocarbon atoms.
 21. The array of claim 20, wherein the amount of fluorinebonded to the carbon atoms of the single wall carbon nanotubes is at thefluorine to carbon ratio of from (a) one fluorine atom to about threecarbon atoms to (b) one fluorine atom to about two carbon atoms.
 22. Anarray comprising: (a) single wall carbon nanotubes; and (b)substituents, wherein the substituents are covalently bonded to thesidewall of the single wall carbon nanotubes.
 23. The array of claim 22,wherein the array is a membrane.
 24. The array of claim 22, wherein theamount of substituent bonded to carbon atoms of the single wall carbonnanotubes is at a substituent to carbon ratio of from (a) onesubstituent to about 26 carbon atoms to (b) one substituent to about twocarbon atoms.
 25. The array of claim 24, wherein the amount ofsubstituent bonded to the carbon atoms of the single wall carbonnanotubes is at the substituent to carbon ratio of from (a) onesubstituent to about ten carbon atoms to (b) one substituent to abouttwo carbon atoms.
 26. The array of claim 25, wherein the amount ofsubstituent bonded to the carbon atoms of the single wall carbonnanotubes is at the substituent to carbon ratio of from (a) onesubstituent to about three carbon atoms to (b) one substituent to abouttwo carbon atoms.
 27. A method comprising: (i) derivatizing a sidewallof the single wall carbon nanotubes with a fluorinating agent; (ii)solvating the derivatized single wall carbon nanotubes in a solvent; and(iii) separating the solvent from the derivatized single wall carbonnanotubes to form a product.
 28. The method of claim 27, wherein theproduct is selected from the group consisting of a paper, a felt, arope, and a mat.
 29. The method of claim 27, wherein the derivatizedsingle wall carbon nanotubes are defluorinated.
 30. The product made bythe process of claim
 28. 31. The product made by the process of claim27.
 32. The method of claim 27, wherein the amount of fluorine bonded tocarbon atoms of the single wall carbon nanotubes is at a fluorine tocarbon ratio of from (a) one fluorine atom to about 26 carbon atoms to(b) one fluorine atom to about two carbon atoms.
 33. The method of claim32, wherein the amount of fluorine bonded to the carbon atoms of thesingle wall carbon nanotubes is at the fluorine to carbon ratio of from(a) one fluorine atom to about ten carbon atoms to (b) one fluorine atomto about two carbon atoms.
 34. The method of claim 33, wherein theamount of fluorine bonded to the carbon atoms of the single wall carbonnanotubes is at the fluorine to carbon ratio of from (a) one fluorineatom to about three carbon atoms to (b) one fluorine atom to about twocarbon atoms.
 35. A method comprising: (i) derivatizing the sidewall ofthe single wall carbon nanotubes with substituents; (ii) solvating thederivatized single wall carbon nanotubes in a solvent; and (iii)separating the solvent from the derivatized single wall carbon nanotubesto form a product.
 36. The method of claim 35, wherein the product isselected from the group consisting of a paper, a felt, a rope, and amat.
 37. The product made by the process of claim
 35. 38. The productmade by the process of claim
 36. 39. The method of claim 35, wherein theamount of substituent bonded to carbon atoms of the single wall carbonnanotubes is at a substituent to carbon ratio of from (a) onesubstituent to about 26 carbon atoms to (b) one substituent to about twocarbon atoms.
 40. The method of claim 39, wherein the amount ofsubstituent bonded to the carbon atoms of the single wall carbonnanotubes is at the substituent to carbon ratio of from (a) onesubstituent to about ten carbon atoms to (b) one substituent to abouttwo carbon atoms.
 41. The method of claim 40, wherein the amount ofsubstituent bonded to the carbon atoms of the single wall carbonnanotubes is at the substituent to carbon ratio of from (a) onesubstituent to about three carbon atoms to (b) one substituent to abouttwo carbon atoms.
 42. The method of claim 1, wherein the step ofassembling comprises assembling an array of the derivatized single wallcarbon nanotubes.
 43. The method of claim 1, wherein the step ofderivatizing the single wall carbon nanotubes facilitates the assemblyof the array of the derivatized single wall carbon nanotubes by enablingthe derivatized single wall carbon nanotubes to move together.
 44. Themethod of claim 42, further comprising removing at least some of thesubstituents from the derivatized single wall carbon nanotubes afterassembly of the array of the derivatized single wall carbon nanotubes.45. The method of claim 42, wherein the substituent comprises fluorine.